Chapter 2 – Network Design. ABB POWER LEADER PMCS Network Architecture

Power Management Control System

Chapter 2 – Network Design


This section describes how to design a Power

Management Control System network on paper so that actual construction and configuration of the network will proceed smoothly.

You need two things for this exercise: a complete list of the IEDs to be networked and a diagram or map of where the IEDs will be located, preferably with realistic distances noted so that wiring runs may be kept within the appropriate limits.

Using the list of IEDs to be networked, refer to Table 1 and note which communications protocols are required

(commnet or Modbus). For Modbus IEDs, note the communications speed at which each IED operates. For

IEDs supporting both protocols, you will need to decide which protocol will be used. Generally, it is preferable to use Modbus rather than commnet unless the Modbus network is at or near capacity for physical IEDs.

When the list of IEDs and the floor plan are in hand, proceed to Section 2–1 for network design rules.

9



2–1 Modbus Rules

The most basic network configuration for PMCS assumes that the software is running on a host PC supporting one or more RS-485 networks on the Modbus protocol. (See

Figure 1 for an example of this configuration.)

Table 2 explains the configuration rules for PMCS networks based on the Modbus platform. Commnet IEDs may be integrated through the Modbus Concentrator (see

Table 4 for commnet wiring rules).

Host PC is based on:

Modbus

Follow these rules for the host…

1. The host PC can support up to 256 independent

Modbus networks. The actual number is determined by the communication cards installed in the host PC

(see below).

2. The Modbus networks are connected to the host PC via an eight-port RS-485 communications card.

3

An option for more limited systems is an RS-

232/RS-485 converter, which permits a single RS-

485 network.

4

3. The host PC must be located at one end of the

Modbus network(s).

And these rules for the attached Modbus network(s)…

1. Each Modbus network supports up to 31 physical Modbus IEDs and up to 247 Modbus addresses. This is possible because commnet IEDs attached to Modbus Concentrators occupy

Modbus addresses but do not create an electrical drain on the RS-

485 network and thus are not counted as physical Modbus IEDs.

2. Each Modbus network must be properly terminated at each end of the network. See Section 2–4.

3. Maximum cable length of each Modbus network is 4000 feet. (See notes on using repeaters to increase this range, Section 2–4. Also, see the note regarding substation installation in Chapter 3.)

4. All Modbus IEDs attached to a single RS-485 network must communicate at the same baud rate. (See Table 1 for Modbus

IEDs’ communication speeds.)

5. RS-485 cable shields must be properly grounded. For maximum protection against surge and EMI damage, each IED on the network should have an isolated ground connection. See Section

2–4, Modbus rule 4, for an example of proper RS-485 wiring and grounding. Also, see the note regarding substation installation in

Chapter 3.

Table 2. Host PC configuration rules.

3

The following RS-485 interface card is recommended for providing the RS-485 connection at the host PC. If any other serial card is used, PMCS requires that the communications driver be compatible with the MS Windows serial communications protocol. Please refer to Section 3–1 for information on the special termination requirements of the RS-485 card.

Manufacturer

Connect Tech, Inc.

Description

Quantity/8 ports

Part, Order Number

Intellicon-Flex8 RS-485 card 1 I4808064XXNC

Intellicon/DFLEX SLIM

8 Port, DB9 I/O Box

4

1

SIMMS

IOB08DB9

4

The following RS-232/RS-485 converter is recommended for providing a single RS-485 connection at the host PC.

Manufacturer Description Part, Order Number

Multilin RS-485/RS-232 Converter F485120

When using the above RS-232/RS-485 converter, remember that the converter has DIP switches inside that determine its baud rate. Switch group 3 should be set according to the baud rate at which the converter is to be used. Refer to the converter’s documentation for further information.

10



2–2 Ethernet Configuration Rules

It is also possible to run the PMCS on a host PC operating on an Ethernet network. If PMCS is running on an

Ethernet-based PC, an Ethernet Gateway is required to communicate with the attached Modbus network(s). (See

Figure 2 for an example of this configuration.)

Recently, IEDs with built-in Ethernet support have begun to become available; PMCS is also capable of supporting these devices. Examples of such devices are the EPM 7700 meter and EPM 9450Q / 9650Q meters. These devices reside on the Ethernet network at the same level as the

Ethernet Gateway.

Table 3 explains the configuration rules for PMCS networks based on the Ethernet platform. Commnet IEDs may be integrated through the Modbus Concentrator.

(See Table 4 for commnet wiring rules.)

EPM 7700 devices require a separate network configuration beyond connecting the devices to the

Ethernet LAN. Please refer to the following PMCS technical documentation for complete network configuration rules and guidelines:

GEH-6514, PMCS Read-This-Book-First. Refer to the section titled “Configuring the EPM 7700 Device Network.”

DEH-40035, GE 7700 Gateway User’s Guide. Refer to the section titled “EPM 7700 Network Configuration.”

EPM9450Q and EPM9650Q devices require separate network configuration beyond connecting the devices to the Ethernet LAN. Refer to the instruction manuals of these devices and to the sections titled “Internal Network

Option.” Also refer to DEH-6510, DDE Server User’s Guide.

Refer to the sections describing the use and configuration of the Modbus TCP Server.

11



Host PC is based on: Follow these rules for the host…

And these rules for the Modbus networks attached to the

Ethernet Gateways…

Ethernet 1. Ethernet Gateway(s) must be used to communicate with non-Ethernet IEDs.

Ethernet-capable IEDs may be installed directly on the Ethernet network at the same level as the Ethernet Gateway(s).

2. The host PC supports up to 64 Ethernet

Gateways.

3. Each Ethernet Gateway supports up to four independent Modbus networks.

The EPM 9450Q /9650Q devices will support one Modbus network.

4. The actual number of IEDs supported by the host varies from system to system, depending on the variety of IEDs used and the number of PMCS data tags required by the IEDs. See GEH-6509,

PMCS DDE Interface Guide,

for details.

5. Ethernet networks should conform to the design guidelines described in

Section 2-3.

1. Each Modbus network supports up to 31 physical

Modbus IEDs and up to 247 Modbus addresses. This is possible because commnet IEDs attached to

Modbus Concentrators occupy Modbus addresses but are not seen as physical Modbus IEDs.

2. Each Modbus network must be properly terminated at each end of the network. See Section 2–4.

3. The Ethernet Gateway must be located at one end of the Modbus network(s).

4. Maximum cable length of each Modbus network is

4000 feet. (See notes on using repeaters to increase this range, Section 2–4. Also, see the note regarding substation installation in Chapter 3.)

5. All Modbus IEDs attached to a single RS-485 network must communicate at the same baud rate.

(See Table 1 for Modbus IEDs’ communication speeds.)

6. RS-485 cable shields must be properly grounded. For maximum protection against surge and EMI damage, each IED on the network should have an isolated ground connection. See Section 2–4,

Modbus rule 4, for an example of proper RS-485 wiring and grounding. Also, see the note regarding substation installation in Chapter 3.

Table 3. Ethernet configuration rules2–3 Ethernet

Network Considerations

This section describes some of the specifications which must be considered when designing an Ethernet network to be used with PMCS.

Note: These specifications are guidelines only and should not be used for actual network design. Consult with a qualified LAN engineer for design requirements that meet your specific installation. The complete specifications are listed in IEEE 802.3 Ethernet. In addition, the National

Electrical Code (NEC) and all applicable local codes must be followed for installing wiring.

Ethernet supports four physical media: 10Base-2

(thinnet), 10Base-5 (thicknet), 10Base-T (twisted pair), and 10Base-FL (fiber). 10Base-T is most common.

12



NOTE for EPM 7700 and 9450Q and 9650Q: The EPM

7700 with Xpress card directly uses either of two types of

Ethernet physical media that must be specified when ordering the meter, 10Base-T, or 10Base-FL. EPM 9450Q and EPM 9650Q must be ordered with 10 Base-T Ethernet

Option. The meters operate in a 10 Mbps system.

A 10Base-T LAN can have a maximum of 1024 devices connected.

Use of repeaters, routers, bridges, gateways, etc.

Repeaters may be used to connect LAN segments and do not determine the boundaries of the LAN. They are used to extend the LAN beyond a single segment. Routers, bridges and gateways may be used to connect the LAN to other LANs or to a WAN.

10Base-T is specified when twisted pair is used and 10Base-

FL is specified where fiber optic cable is used. While media converters are available to allow the use of both twisted pair and fiber optic cable in the same LAN, and can be used to extend the length of the LAN, they are beyond the scope of this discussion.

CAUTION:

The recommended installation practice is to implement optical fiber for connections between buildings to provide electrical isolation. This eliminates harmful ground loops caused by differences in the ground potential between structures.

CAUTION: data communication lines. Data line surge protection is not required for fiber optic connections.

Data line surge protection is recommended for network components such as hubs, computers, or modems connected to IEDs with copper wire, especially installations where the data communication cable is exposed (i.e., not encased in conduit) or runs parallel to power conductors. PMCS IEDs are routinely installed in areas exposed to heavy electromagnetic fields

(EMF), which can induce damaging surges in

10Base-FL specifications and rules

Maximum/Minimum length of segments

For a 10Base-FL LAN, the maximum length of a segment is

2000 meters (6500 ft). The minimum length of any cable is 2.5 Meters or about 8 ft. This minimum length is of particular concern when a device is located in close proximity to the hub.

Maximum number of segments

A 10Base-FL LAN can consist of up to 5 segments using 4 repeaters. However, only three of these segments can have devices connected.

Maximum number of devices

A 10Base-FL LAN can have a maximum of 1024 devices connected.

Use of repeaters, routers, bridges, gateways, etc.

Repeaters may be used to connect segments and do not determine the boundaries of the LAN. They are used to extend the LAN beyond a single segment. Routers, bridges and gateways may be used to connect the LAN to other

LANs or to a WAN.

10Base-T specifications and rules

10Base-T Ethernet uses CAT 3, 4 or 5 twisted pair cable, depending on the installation.

Maximum/Minimum length of segments

For a 10Base-T LAN, the maximum length of a segment is

100 meters (328 ft). The minimum length of any cable is

2.5 Meters or about 8 ft. This minimum length is of particular concern when a device is located in close proximity to the hub.

Maximum number of segments

A 10Base-T LAN can consist of up to 5 segments using 4 repeaters. However, only three of these segments can have devices connected.

Maximum number of devices

13



2–4 Commnet Configuration Rules

POWER LEADER commnet IEDs may be integrated into a

PMCS network through a special Modbus IED called the

Modbus Concentrator. The rules outlined in Table 4 apply to using commnet IEDs with PMCS, regardless of whether the host PC is operating on an Ethernet or Modbus network. (See Figures 3 and 4 for examples of commnet

IEDs operating on PMCS.)

Rules regarding:

Modbus

Concentrator limitations

Commnet IED configuration rules:

1. Each Modbus Concentrator supports up to eight commnet segments.

2. Each commnet segment supports up to four commnet IEDs.

3. Only one waveform-capturing meter (POWER LEADER Meter) is allowed per commnet segment.

4. POWER LEADER Repeaters and Junction/Outlet Boxes do not count toward the four-IED-per-segment limit.

5. No connections between commnet segments are permitted. Each segment must be wired independently (having no contact with other commnet segments) and connected to the Concentrator at one point only (no loops permitted).

Reference

Figure:

Figure 15

Figure 15

No figure provided

Figure 19 and

Figure 20

Figure 28 –

Figure 32

Commnet wiring limitations

1. Maximum cable length of a commnet segment is 1000 feet. Maximum range between commnet IEDs on a segment is 1000 feet (except for repeaters; see below).

2. In no case may a commnet IED be wired more than 1000 feet from the Modbus

Concentrator or a POWER LEADER Repeater.

3. POWER LEADER Repeaters may be used to extend the range of commnet segments. A repeater regenerates the commnet signal to its original strength, allowing it to travel up to another 1000 feet.

4. Long-distance segments may be created by placing multiple repeaters adjacent to one another in a commnet segment. A repeater communicating directly with another repeater may span up to 6000 feet.

5. Maximum allowable cable length of a single commnet segment is 12,000 feet, which may be constructed with any allowable combination of repeaters and IEDs.

6. For ease and economy of wiring, the POWER LEADER Junction/Outlet box may be used to create nodes of commnet IEDs with a common wiring point to be connected to the Modbus concentrator. The POWER LEADER Junction/Outlet

Box allows the interconnection of as many as four shielded, twisted-pair cables to create this common wiring point. For instance, rather than a daisy-chain of wiring in a lineup from one meter or trip unit to the next, up to four IEDs may be wired to the POWER LEADER Junction/Outlet Box, which is then connected to the Modbus Concentrator.

Figure 16

Figure 16

Figure 17

Figure 18

No figure provided

Figure 19 and

Figure 20

Table 4. Commnet IED configuration rules.

14



2–5 Modbus Wiring Rules – Diagrams

The Modbus network protocol has wiring rules and limits on the number of IEDs that may be attached.

This section describes in greater detail the rules you must follow when designing a Modbus network.

1. Each RS-485 network may support up to 31 Modbus

IEDs. Figure 7 illustrates this rule. (See the

exception below Figure 6.)

Host

WARNING:

Network wiring and grounding rules described herein apply primarily to commercial/industrial installations. Substation installations will exist in the presence of dangerously elevated ground potential relative to points outside of the station grid as well as large electromagnetic induction fields. Additionally, large ground faults can elevate substation ground potentials. Follow local utility bestpractices/safety procedures to prevent

risk of

shock/electrocution to personnel and damage to equipment that could result in a loss of protection and communications.

NOTE:

It is important to take future expandability into consideration when designing a network configuration. This is particularly so when the network is near its maximum number of IEDs or maximum cable length. Adding IEDs to a network after it has been installed may require rewiring the network.

31 RS-485 IEDs maximum;

PMCS Host PC, Ethernet Gateway or MSP always located at one end of Modbus network.

Figure 7. Network illustrating Modbus Rules 1 and 2.

Exception to Rule 1: Some types of IEDs must be wired on dedicated private serial network segments, one IED per serial Modbus line.

2. The host (or Ethernet Gateway) must always be located at one end of any Modbus segment. It may not be located in the center of a Modbus network.

Figure 7 shows the correct placement of the host

(PC or Ethernet Gateway).

3. All Modbus IEDs on a single RS-485 network must communicate at the same baud rate. If IEDs with different communication speeds are connected to the same RS-485 network, the whole segment will

communicate at the speed of the slowest IED. Figure

8 illustrates this rule. (Communication speeds for

supported IEDs are listed in Table 1.)

CAUTION:

Wire-run distances mentioned in the configuration rules assume application above grade or in conduit. For below-grade applications, refer to Section 3–1, Wiring

Requirements.

Regardless of which platform is supporting the RS-485 networks (Ethernet Gateway, RS-485 card, or RS-232/RS-

485 converter), the following rules apply to each individual RS-485 network.

Figure 8. Network illustrating Modbus Rule 3.

4. Each RS-485 network must be properly terminated at both ends of the cable run after the final IED.

(See Section 3–1 for details on termination.) Figure

9 illustrates this rule.

15



5. Each RS-485 network must have its shield properly

grounded. Figure 9 illustrates proper RS-485 wiring

and grounding.

RS-485 Host

(RS-485 card*, RS232/RS-485 converter,

Multiple Serial Port or Ethernet Gateway RS-485 port)

Network Connections: + Shield

CAUTION:

Improper grounding may create a ground-loop condition and cause communications failures. Make sure you follow the wiring diagram carefully.

To ensure proper grounding, follow this procedure.

Begin by grounding the RS-485 cable shield at the host. Follow the cable to the first IED on the network. Do NOT connect the cable ground to the

IED. Pick up the RS-485 output cable from the IED and attach its ground to the IED’s shield connection or grounding screw. For IEDs with no grounding connectors, connect to earth ground.

Follow the cable to the next IED, and repeat the above procedure. Do not connect the RS-485 shield from the previous IED, but DO connect the RS-485

OUT shield on its way to the next IED.

RS-485

Two wire, twisted, shielded pair cable

RS-485 IED #1

Shield

+

-

RS-485 IED #2

Shield connected at host

120-ohm terminating resistor

* Connect Tech RS-485 cards require a 600-ohm resistor in place of the 120-ohm terminating resistor.

Shield not connected at first IED

RS-485 IN

Shield connected at first IED

RS-485 OUT

Shield not connected at IED

RS-485 IN

EXCEPTION:

The Multilin 565 Feeder

Management Relay does not have isolated communications ports. Do NOT connect the shield at this IED. Instead connect the shield of the incoming RS-485 cable to the shield of the outgoing RS-485 cable, skipping the Multilin 565.

Rules of thumb

: RS-485 cable ground should always be connected at the previous IED, never upon arrival at an IED. All RS-485 IEDs must have either two communications cables attached or one communications cable and a terminating resistor.

Shield

+

-

Shield connected at IED

RS-485 OUT

RS-485 IED #31

Shield not connected at IED

RS-485 IN

Shield

+

-

120-ohm terminating resistor

Figure 9. Network illustrating Modbus Rules 4 and 5.

6. A single RS-485 network may have up to 215 commnet IEDs attached to it via POWER LEADER

Modbus Concentrators. Figure 10 illustrates this

rule.

16

Host

MC

RS-485 IEDs

(31 Max)

Modbus

Concentrator

Commnet IEDs

(up to 32 per Modbus Concentrator,

215 total per RS-485 network)



9. There may be no more than two RS-485 repeaters

between any two RS-485 IEDs. Figure 13 illustrates

this rule.

Rptr Rptr

Correct - Maximum two repeaters between RS-485 IEDs

Rptr Rptr Rptr

Incorrect - more than 2 repeaters between RS-485 IEDs



7. A single RS-485 network may have no more than

4000 feet of cable (total cable length, not distance

between IEDs). Figure 11 illustrates this rule.

Host

100 ft 200 ft

Total Cable Length < 4000 feet

RS-485 IEDs

(31 Max)

300 ft

1500 ft

300 ft

1500 ft


8. RS-485 repeaters may be used to extend the range beyond 4000 feet. A single RS-485 repeater may be used to provide a 4000-foot extension, and each additional repeater in a sequence extends the range

by another 4000 feet. Figure 12 illustrates this rule.

NOTE ON DUAL-PORT RS-485 IEDS:

Several of the Multilin power management IEDs offer two RS-485 ports on the same IED. Do not connect both RS-485 ports to a PMCS network.

The same data are available from both RS-485 ports and will cause conflicts if the PMCS attempts to access both ports simultaneously.

However, the Modbus Monitor’s wiring scheme is slightly different from the Multilin scheme. The dual-port version of the POWER LEADER

Modbus Monitor MUST be connected to two separate RS-485 networks. See Rule 10 for details.

10. Modbus Monitors (dual-port version) may not be wired in any configuration other than the four

shown in Figure 14. Although the Monitor’s RS-485

ports have separate addresses, you may NOT wire the same Modbus network to both ports. A two-port

Modbus Monitor must be wired to two separate

Modbus networks.

NOTE

: For more information on wiring the

POWER LEADER Modbus Monitor, refer to

DEH-027, Modbus Monitor User’s Guide.

Host

100 ft

With 2 Repeaters,

500 ft

Total Cable Length < 8000 feet

700 ft

RS-485

Repeaters

R

4000 ft

R

200 ft

2500 ft


17



Example A

Modbus

Segment A

Monitor

#1

Example B

Modbus

Segment A

Modbus

Segment B

Monitor

#1 makes this concern irrelevant for examples A, B, and D, since in Example A you could have either a single- or a dual-port Monitor, while in

Examples B and D you may only use a dual-port monitor(s).

Example C

Modbus

Segment A

Monitor

#1

Example D

Modbus

Segment A

Modbus

Segment B

Monitor

#1

Monitor

#2

Monitor

#2

Figure 14. Valid Modbus Monitor network architectures.

CAUTION:

Any other wiring of the Modbus

Monitor may result in incorrect operation and errors.

CAUTION DUAL PORT MONITOR USERS: Do not connect the Monitor’s two RS-485 ports to the same

Modbus segment.

This will cause communication errors and possibly damage the Monitor.

Example A shows a single Modbus Monitor wired to one

Modbus segment. Example B shows the same monitor in a dual-port version, wired to two different Modbus segments.

Examples C and D illustrate fully loaded Modbus segments. No more than two Monitors are permitted on any Modbus segment.

Example C illustrates a pair of Monitors connected to a single Modbus segment. In this example, the Monitors may be either single port or dual-port versions, provided both are the same version (see note below). Example D shows the same pair of Monitors wired to a second Modbus segment.

CAUTION:

With regard to Example C (two

Monitors on a single RS-485 segment), it is not permissible to mix different models of Monitors on a segment. Monitors #1 and #2 must be of the same model, either both single-port or both dualport.

The nature of the other network architectures

18

2–6 Commnet Wiring Rules – Diagrams

POWER LEADER commnet IEDs may be integrated into

PMCS through the use of the POWER LEADER Modbus

Concentrator, which collects data from commnet IEDs and communicates that data across the RS-485 network.

Each Modbus Concentrator supports up to eight commnet segments. Each commnet segment may accommodate up to four commnet IEDs. The following are the basic rules to ensure proper network operation for POWER LEADER commnet IEDs. Note that these rules apply only to individual commnet segments of a POWER LEADER

Modbus Concentrator, not to the RS-485 network.

1. Each Modbus Concentrator supports up to eight commnet segments. Each commnet segment may support up to four commnet IEDs, only one of which may be a waveform-capturing meter. POWER

LEADER Repeaters and Junction/Outlet Boxes are

not counted as commnet IEDs. Figure 15 illustrates

this rule.


Chapter 2 – Network Design degrades and the danger of errors rises to an unacceptable level. The Repeater regenerates a signal to its original strength, allowing it to travel up to another 1000 feet. Thus, each Repeater can add up to 1000 feet of range to the commnet segment.

For example, a segment containing a single

Repeater may have no more than 2000 feet of total cable length. No more than 1000 feet of cable are permitted between the Modbus Concentrator and the first Repeater or between the Repeater and the

last IED on the segment. Figure 17 illustrates this

rule.

CAUTION:

In no case may there be more than

1000 feet of cable between any two commnet

IEDs other than Repeaters. At ranges over 1000 feet, commnet signals become degraded and communication errors may result.

Modbus

Concentrator

4 commnet IEDs/segment max

Modbus

Concentrator

400 ft

600 ft

R

200 ft

600 ft

Max length of a commnet segment with one Repeater < 2000 feet

200 ft

Figure 17. Network illustrating commnet Rule 3.

4. Long-distance cable runs may be built by placing two

Repeaters adjacent to one another in the segment. A pair of adjacent Repeaters has a range of up to 6000

feet of cable. Figure 18 illustrates this rule.


2. A commnet segment may have no more than 1000 feet of cable between the Modbus Concentrator and the final IED on a segment. (Repeaters may be used

to extend this range; see Rule 3.) Figure 16

illustrates this rule.

Modbus

Concentrator

300 ft

200 ft

200 ft

200 ft

Max length of a commnet segment < 1000 feet


3. The maximum communication range of commnet

IEDs (including the Modbus Concentrator’s commnet ports) is 1000 feet, after which its signal

1000 ft

Modbus

Concentrator

400 ft

600 ft

R

6000 ft

R

600 ft

200 ft

Max length of a commnet segment with two Repeaters < 8000 feet

200 ft

R R

R

6000 ft

4000 ft

1000 ft

Ma x len gth of a com m ne t segm ent with th ree R e pea ter s < 12 000 fe et

(note: only o ne othe r IE D m ay be use d o n a co m m n et segm ent w ith th ree rep eaters)


5. The maximum allowable cable length of a single commnet segment is 12,000 feet. This may be

19


Chapter 2 – Network Design achieved with any allowable combination of

Repeaters and IEDs.

6. For ease of wiring, the POWER LEADER

Junction/Outlet Box may be used to create nodes of commnet IEDs with a common wiring point to be connected to the Modbus concentrator. The

POWER LEADER Junction/Outlet Box allows the interconnection of as many as four shielded, twistedpair cables to create this common wiring point. This can be of great help in economizing on wiring and offering greater flexibility in network design. For instance, rather than a daisy-chain of the wiring in a lineup from one meter or trip unit to the next, up to four IEDs may be wired to the POWER LEADER

Junction Box, which is then connected to the

Modbus Concentrator.

Examples of the use of a POWER LEADER Junction

Box with the Modbus Concentrator are provided in

Figure 19 and Figure 20. Junction Boxes are not

counted as IEDs for purposes of the four IED per

commnet segment limit. Figure 19 is an example of

a Junction Box used to create a node connecting four commnet IEDs to a Modbus Concentrator.

Figure 20 is an example of a Junction Box with

Repeaters, observing the four IED per segment limit

(the two Repeaters and the Junction Box do not count as IEDs).

commnet

IED

CAUTION:

The four-IED-per-segment limit must be observed at all times. Although the POWER

LEADER Junction Box has terminals to accept up to 12 commnet lines, do NOT connect more than four commnet IEDs to a single Junction

Box or Modbus Concentrator commnet segment.

to

Modbus

Concentrator

Junction

Box commnet

IED commnet

IED commnet

IED


to

Modbus

Concentrator commnet

IED

Junction

Box

Long-range commnet segment

POWER

LEADER

Repeater

POW ER

LEADER

Repeater commnet

IED commnet

IED commnet

IED


20



2–7 Performance Recommendations

Although a PMCS network will function as long as all the rules in the previous section are followed, you can enhance performance by considering the following recommendations for Modbus, commnet.

The Ideal Network

Theoretically, a single Modbus IED or 40 commnet IEDs distributed across five Modbus Concentrators (one IED per commnet segment) yields maximum performance.

Naturally, in the real world few networks will fall into this precise configuration. To extract maximum performance from the PMCS, follow the performance recommendations below.

Modbus performance recommendations

1.

Use multiple RS-485 networks if possible, depending on the RS-485 connection at the host. If using an eight-port RS-485 card or an Ethernet Gateway (four ports) for connection to the network, you can improve performance by using the full number of ports available, rather than burdening a single RS-485 port.

Distributing the IEDs across all available RS-485 ports permits the communications load to be distributed rather than asking a single network to carry the full load.

2.

Divide the IED loads evenly when distributing IEDs across multiple RS-485 networks.

3.

Pay careful attention to Modbus Rule 2, regarding the communication speeds of IEDs on a given network.

Although a network will function with mixed IEDs, its communication speed will be dragged down to the lowest common denominator. Thus, a single 2400baud IED forces the entire network to communicate at

2400 baud, regardless of the presence of any 19.2kbaud IEDs.

Commnet performance recommendations

1.

Modbus is preferred over commnet where either protocol is available. This is the case for the POWER

LEADER Electronic Power Meter and the POWER

LEADER MDP Overcurrent Relay. Each of these IEDs offers a Modbus communications option.

2.

Minimize the number of commnet IEDs per segment.

The Modbus Concentrator is a polling IED, meaning that it queries each commnet segment continuously and in order asking for information. It then stores the information until it is asked by the PMCS to transmit its data to the host. If the number of commnet IEDs is unevenly distributed, the Concentrator takes longer than necessary to poll each segment.

3.

Keep data-intensity in mind when connecting more than eight commnet IEDs to a single Modbus

Concentrator. If it is necessary to connect more than eight commnet IEDs to a single Modbus Concentrator, one or more segments will be supporting multiple

IEDs. Keep the following list in mind when selecting which IEDs to double up on the same commnet segment. The best choices for doubling up are listed first.

1. Spectra MicroVersaTrip trip unit

2. Enhanced MicroVersaTrip-C and -D trip units

3. POWER LEADER MDP Overcurrent Relay

4. Spectra Electronic Control Module

5. POWER LEADER Electronic Power Meter

6. POWER LEADER Meter

IEDs at the top of the list are less data-intensive and easier for the Concentrator to poll. IEDs at the bottom of the list are very data-intensive and, if possible, should be given their own commnet segment. In other words, if you must put multiple IEDs on a segment, it is preferable to put low-demand IEDs together on a segment and try to keep high-demand IEDs on their own segments. Try to distribute the high-demand

IEDs across the available segments, keeping the number of high-demand IEDs per segment evenly distributed.

2–8 Addressing the IEDs

Each IED attached to a PMCS network must have a unique address. Prior to installing any wiring, you should plan the addresses for the IEDs to avoid any conflicts. Keep in mind these important points when assigning network addresses.

• Keep a table of IED names and addresses to avoid conflicts and to help with host configuration. Table 5 summarizes Modbus addressing considerations, based on the following rules.

- Modbus Concentrator addresses must be in the range of 1 to 32.

- Modbus-native IEDs other than the Concentrator may occupy any address from 1 to 247.

- Commnet IEDs must have Modbus-equivalent addresses in the range of 33 to 247.

- The host PC does not require an address due to the master-slave organization of the PMCS.

21



Modbus

Address

NOTE:

Per the EIA485 standard, each RS-485 network supports up to 32 “drops” or electrical drains on the network. However, the Ethernet

Gateway or RS-485 interface card counts as one drop. Thus, only 31 other IEDs may be attached to each RS-485 network, even though 32 Modbus addresses are available for use. Also, unlike commnet’s POWER LEADER Repeaters, RS-485 repeaters are counted as IEDs because although they have no Modbus address, they do act as a drop on the network.

Appropriate Usage/Supported IEDs

0 • Broadcast (not available to user)

1 – 32 • Modbus Concentrators must have addresses in this range

• Other Modbus native IEDs may also have addresses in this range

33 – 247 • Modbus native IEDs may have addresses in this range

• Commnet IEDs must have addresses in this range

Table 5. Modbus address range appropriate usage.

• Commnet IEDs are preprogrammed with a factory-set address. You must change this address immediately upon installation of the IED. Refer to the IED’s user manual for instructions on assigning an address.

• Because the commnet network accepts a different range of addresses than the Modbus network, commnet addresses must be mapped to corresponding Modbus addresses. The formula for this mapping is: desired Modbus address + 267 = commnet address to set at IED

. For example, to set a commnet

IED to Modbus address 33, the commnet address set at the IED must be 300. Table 6 illustrates address mapping.

For Modbus Address:

33

34

35

...

246

247

Set commnet IED Address to:

300

301

302

...

513

514

Table 6. Modbus-to-commnet address mapping.

- You may want to block commnet address assignments by lineup and/or Modbus Concentrator segment. For example, start with 40 for the first lineup attached to one Modbus Concentrator, 50 for the second lineup attached, and so on. Addresses must be in the range

33 to 247. The example presented in Figure 18 demonstrates this.

- Increment the individual IEDs in each lineup by one.

For example, if the first IED in a lineup is Modbus address 101, the second IED should be 102, the third

IED should be 103, etc.

• Addresses may be entered or changed at any time that control power is present.

Figure 21 illustrates a sample network with IED addresses;

Table 7 provides details of the IEDs shown in Figure 21.

22



Figure 21. Sample network with IED addresses.

23



Equipment

Lineup 1

POWER/VAC Medium-Voltage

Switchgear

Lineup 2

8000-Line Motor Control Center

Lineup 3

AKD-8 Low-Voltage Switchgear

Attached

IEDs

Modbus Concentrator 1

Segment 1

POWER LEADER Electronic Power Meter

MDP Overcurrent Relay with commnet



Segment 2



Segment 3



Segment 4



EPM 7700 Electronic Power Meter

Multilin 269 Plus Motor Relay


Segment 1

- Spectra Electronic Control Module

Segment 2 -

Spectra Electronic Control Module

Segment 3 -


Segment 4 -


EPM 7700 Electronic Power Meter using IP address =

3.46.9.102


Segment 1

- POWER LEADER Meter

Segment 2

- Enhanced MicroVersaTrip trip unit

Segment 3

- POWER LEADER Meter

Segment 4 -

Enhanced MicroVersaTrip trip unit

Lineup 4

Medium-Voltage Motor Control Center

Lineup 5

Substation

GE Fanuc Programmable Logic Controller 90/30

Multilin 565 Feeder Management Relay

EPM 5300P

EPM 5200P

EPM 9650Q

EPM 7300

EPM 7330

EPM 7330

Table 7. IED-addressing scheme for Figure 21.

Commnet

Address

—

302

303

304

305

307

308

312

313

317

318

—

—

—

332

337

352

357 n/a

—

—

—

—

—

—

—

422

427

432

437

442

447

452

—

—

Modbus

Address

001

035

036

037

038

040

041

045

046

050

051

052

060

002

065

070

085

090 n/a

200

205

210

215

220

225

003

155

160

165

170

175

180

185

004

005

24



2–9 Multiple RS-485 Networks – Addressing

PMCS supports up to 256 independent Modbus networks.

Regardless of how many RS-485 networks are connected, the addressing concepts regarding multiple RS-485 networks remain the same. Each RS-485 network is addressed independently of the others. Thus, Network 1 may have an IED with Modbus address 20, and Network 2 may have an IED with Modbus address 20 without conflict.

The PMCS will be aware that they are different IEDs, much as the postal system delivering mail realizes that 17

Mulberry Lane in Town A is a different address than 17

Mulberry Lane in Town B.

2–10 System Expansion

Whenever new IEDs are added to the network, be sure to observe these points:

• Follow the proper installation procedures.

• Ensure that the system configuration rules have been followed.

• All new IEDs are shipped with the same default address. To avoid conflicts, change the address of each new IED immediately upon installation to an unoccupied address in the PMCS networks.

2–11 Case Studies

Five case studies are provided as examples of how to design a network based on PMCS. In each case, a fictitious company called GHO Corp. is installing a power management system based on PMCS.

In Case One, GHO Corp. has only a few Modbus RTUbased IEDs that it would like to network to the PMCS software for remote control and viewing of power consumption and alarms.

In Case Two, GHO Corp. wishes to expand the Modbus network it developed in Case One by adding some commnet IEDs to the network.

In Case Three, GHO Corp. already has an existing network based on Ethernet and would now like to integrate a power management system with this network.

GHO Corp. still has only a few Modbus RTU-based IEDs that it would like to network to the PMCS for remote control and viewing of power consumption and alarms.

Now, however, it wants the host to be based on Ethernet rather than Modbus, which requires the use of an

Ethernet Gateway.

In Case Four, GHO Corp. wishes to install a PMCS power management system using both Modbus- and commnetbased IEDs, with the host based on Ethernet.

Case Five demonstrates the use of dual-port RS-485 IEDs in a Modbus network, showing the differences between the

Multilin dual-port IEDs and the POWER LEADER

Modbus Monitor, which also provides two RS-485 ports.

Case Study One

GHO Corp. has assigned its plant engineer, Bill, the task of designing and installing a simple power management system. GHO Corp. wishes to use PMCS to monitor and control several Modbus power management IEDs.

Bill’s first task is an easy one. He must choose a platform on which the PMCS host will reside. Using the flowchart in

Section 1-1, he makes his decision. There is no existing

Ethernet network in his facility, nor are there any plans for one. Bill chooses Modbus as his basic platform for the

PMCS.

Next, Bill makes a list of the IEDs that GHO Corp. wants to include on their PMCS network:

• One PLC 90/30 Programmable Logic Controller for process control

• Three EPM 3720 Meters for monitoring power

• One Multilin 269+ Motor Relay for motor protection

• One Multilin 565 Feeder Management Relay for feeder protection

He checks the list of communications protocols in Table 1 and notes that all of the IEDs communicate on Modbus; because no commnet IEDs are being used, no Modbus

Concentrators are needed. The Modbus IEDs communicate at different baud rates, though, and Bill makes a note that they should be placed on separate RS-

485 networks for improved performance.

Bill now turns to his floor layout to see just where the wiring could be run and how many feet of cable will be needed. He maps where his IEDs must be located and where the host PC will sit. He measures the cable runs required to connect the IEDs to the host PC, keeping in mind that the wiring rules require him to daisy-chain the

IEDs on each RS-485 network one after another. His floor

layout is shown in Figure 22.

25



Bill's Office

300'

Terminating

Resistors

Lathe Area

EPM 3720

Electronic Power Meter

350'

RS485 networks terminated at host PC

Bill's Office

Network 4 - 19.2 kbaud

100'

Lathe Area

EPM 3720


350'

Milling Area

Multilin 565

Feeder Management Relay

Main power feed

350'

Milling Area

EPM 3720



Multilin 565

Feeder Management Relay at main power feed

600'

EPM 3720


Machining Area

550'

Multilin 269+

Motor Relay

Assembly Line Area

200'

Machining Area

EPM 3720


PLC 90/30

Programmable Logic Controller

550'

GHO Corp Machine Shop network wiring diagram

Figure 22. Floor layout for Case One.

600'

Multilin 269+

Motor Relay

Terminating

Resistors

Assembly Line Area

EPM 3720


PLC 90/30



550'

Figure 23. Redesigned layout for Case One.

Bill’s calculates his total cable length at 2300 feet, well short of the 4000-foot limit.

Next, Bill checks Table 2 for the Modbus wiring rules.

Proper termination is required at each end of the network, and is provided at the RS-485 card by attaching jumpers to the correct pins (see RS-485 card user manual). The appropriate terminating resistors must be used at the opposite end of each RS-485 network, per Section 2–4, rule

3.

His cable length is well under the 4000-foot limit, so no repeaters will be needed.

Because he has only six IEDs to connect, only one RS-485 network is required, and thus an RS-232/RS-485 converter would do the job. However, he considers the performance recommendations given in Section 2-6 and, remembering his earlier note about the different baud rates of his

Modbus IEDs, he decides to distribute the IEDs across four ports of an RS-485 network card, so that he can place IEDs with matching baud rates on the same RS-485 network.

The system redesigned for optimum performance is shown

in Figure 23.

Confident that his new design will provide maximum performance, and with his wiring requirements and limits met, Bill moves on to select Modbus addresses for the IEDs.

He checks Section 2-7 and sees that he can assign his IEDs any Modbus address between 1 and 247. He selects addresses and records them for future reference. The

address chart is shown in Table 8.

IED Type

PLC 90/30

EPM 3720

EPM 3720

EPM 3720

Multilin 269+

Multilin 565

Physical Location

Assembly line

Milling

Lathe area

Machining

Assembly line

Power intake area

Modbus Address

01

02

03

04

05

06

Table 8. IED Addresses for Case One.

Chapter 3 provides Bill with physical wiring requirements and rules. He finds that he’ll have to use Belden 3074F cable, readily available. He also locates the correct terminating resistors at both ends of each RS-485 network.

He installs the IEDs according to the instructions in the user manual for each IED. He then makes connections to the RS-485 communications cable in daisy-chain fashion, one IED to the next, terminated at each end of each RS-

485 network, double-checking his wiring against the example provided in Section 2–4.

He must also bear in mind proper shield-grounding considerations – each RS-485 IED grounded at only one

26


Chapter 2 – Network Design point and no two IEDs’ grounds connected (Rule 4,

Section 2-4).

Bill assigns a Modbus address to each IED. He then sets communication speeds and functional and protective parameters according to the instructions in each user manual.

Bill installs the PMCS software at the host PC and configures IED addresses at the host to match the addresses assigned to each on the network.

When all connections have been made and the IEDs and software are appropriately configured, Bill applies power to the system and runs tests to assure that everything is functioning properly.

If any difficulties are encountered, Bill refers to the trouble-shooting guide in Chapter 4.

Case Two

Case Two begins where Case One left off. The Modbus network is in place and GHO Corp. has been so pleased with their new PMCS system that they now wish to tie in a second building (Facility Two) and add several additional power management IEDs. However, the IEDs they wish to add are all commnet IEDs.

The host platform is based on Modbus, with a multi-port

RS-485 interface card providing the connection to the networks. Knowing the host platform and its currently attached IEDs, Bill makes a list of the IEDs that GHO

Corp. want to add to their PMCS network. His list of additional IEDs is:

• Six Enhanced MicroVersaTrip trip units for equipment protection

• Three POWER LEADER Meters for waveform capture

• One POWER LEADER EPM

• One POWER LEADER MDP Overcurrent Relay

• One Spectra Electronic Control Module

Commnet IEDs require Modbus Concentrators to be recognized by the PMCS. Bill has nine commnet IEDs to connect, so he will need only one Modbus Concentrator

(each Concentrator supports up to 32 commnet IEDs).

However, with some of the commnet IEDs located in

Facility Two, well beyond the 1000-foot segment limit, Bill realizes that he must either locate the Modbus

Concentrator in Facility 1 and run several very long commnet segments using POWER LEADER Repeaters to span the long runs or place a Modbus Concentrator in

Facility Two and extend his RS-485 network over to Facility

Two with RS-485 repeaters. Bill decides that it will be easier and more cost effective to run a single long RS-485 segment with a pair of RS-485 repeaters than to extend six commnet segments. An added benefit: each repeater uses optical isolation between its incoming and outgoing lines, eliminating harmful ground loops that can result when the ground potential between two structures is different.

For even greater electrical isolation Bill could have used an optical fiber link between the two remote locations.

Bill turns to his floor layout, to see just where the wiring could be run and how much distance it must cover. He knows where his host PC is located and realizes that he will have to interrupt the Modbus network at one or more locations to insert Modbus Concentrators to support his commnet IEDs. He maps where his IEDs must be located and, based on this information, where the Concentrators will be mounted. Next he plans the commnet segments and measures the cable runs required for each segment to connect the IEDs to the Modbus Concentrator, keeping in mind that the commnet rules require him to daisy-chain the IEDs one after another (unless he uses a

Junction/Outlet box). His floor layout is shown in Figure

24.

27



RS485 networks terminated at host PC

Bill's Office


300'

100'


Multilin 565


Facility Two

EPM 3720

600'

Multilin 269

Assembly Line Area

PLC 90/30


550'

RS485 repeater

Terminating

Resistor

Commnet Segment 1

PLEPM EMVT

Segment 2

EMVT EMVT

EPM 3720

600'

Long-range RS485 cable run

3500 feet

RS485 repeater


Lathe Area

EPM 3720

Machining Area

Terminating

Resistor

Figure 24. Floor layout for Case Two.

350'

Milling Area

Modbus

Concentrator

Segment 3

Segment 5

EMVT EMVT POWER

LEADER

Meter

Segment 4

MDP POW ER LEADER

Meter

POWER

LEADER

Meter

EMVT ECM

IED Type

PLC 90/30

EPM 3720

EPM 3720

EPM 3720

Multilin 269+

Multilin 565

Modbus

Concentrator

Enhanced

MicroVersaTrip

Enhanced

MicroVersaTrip

Enhanced

MicroVersaTrip

Enhanced

MicroVersaTrip

Enhanced

MicroVersaTrip

Enhanced

MicroVersaTrip

POWER

LEADER Meter

POWER

LEADER Meter

POWER

LEADER Meter

POWER

LEADER EPM

MDP

Overcurrent

Relay

Spectra ECM

Physical Location

Assembly line

Milling

Lathe area

Machining

Assembly line

Power Intake area

Facility 2, north wall

Facility 2, Segment 1












Table 9. IED Addresses for Case Two.

Modbus Address

01

02

03

04

05

06

10

33

34

35

36

37

38

39

40

41

42

43

44

He must also bear in mind proper shield grounding considerations – each RS-485 IED grounded at only one point and no two IED’s grounds connected (Rule 4,

Section 2-4).

Bill checks Table 4 for the commnet wiring rules and finds that he must keep his POWER LEADER Meters on separate commnet networks, limit his commnet IEDs to four per segment, and keep each segment under 1000 feet

(unless he uses repeaters). The commnet segments he has planned satisfy all these rules.

Because his cabling limits are met, Bill selects Modbusequivalent addresses for the IEDs and adds them to his address chart for future reference. His updated address

chart is shown in Table 9.

Bill next checks Chapter 3 for physical wiring requirements and rules. He knows he needs Belden 3074F cable for the new RS-485 wiring to extend RS-485 Network

3 to the RS-485 repeater for the jump to Facility Two and to make the connection to the Modbus Concentrator from the RS-485 repeater in Facility Two. He moves the terminating resistor from the end of RS-485 Network 3 out to the new end at the Modbus Concentrator in Facility

Two.

28



Commnet wiring requires Belden 8719 cable. Bill installs the IEDs according to the instructions in each user manual. He wires each commnet segment in daisy-chain fashion, one IED to the next, being sure to ground the shield at the Modbus Concentrator only.

Bill then sets local addresses on the IEDs in accordance with the addressing rules in Section 2–6. He sets communication speeds and parameters according to the instructions in each user manual.

Bill installs the PMCS software at the host PC and configures the IED addresses.



have different communication speeds. For performance reasons, Bill decides to break the IEDs off to independent networks rather than connect all of them to the same RS-

485 network. The Ethernet Gateway offers four RS-485 ports, so using more than one port poses no additional cost burdens or configuration concerns.

Bill turns to his floor layout, to see just where the wiring could be run and how much distance it must cover. He maps where his IEDs must be located and where the

Ethernet Gateway will sit. He then measures the cable runs required to connect the IEDs to the Ethernet Gateway, keeping in mind that the RS-485 rules require him to daisy-chain the IEDs one after another. His floor layout is

shown in Figure 25.

Ethernet

RS485 networks terminated at Ethernet Gateway


Bill's Office

Ethernet

Gateway

150'

Lathe Area

Network 1 -

9600 baud

150'

Multilin SR745

Transform er

Managem ent Relay


Multilin 565


600'

350'

Milling Area

Multilin SR469

Motor Management Relay

Machining Area

Case Three

In Case Three, GHO Corp. has an existing Ethernet network installed and would now like to add power management capabilities with PMCS. Once again, plant engineer Bill has been given the task of designing and installing this system.

As before, Bill’s first task is to choose a platform on which the PMCS host will reside. Using the flowchart in Section

1-1, he decides that the PMCS will reside on Ethernet, requiring one or more Ethernet Gateways to communicate with the RS-485 networks.

Next, Bill makes a list of the IEDs that GHO Corp. needs to support on their PMCS network. The IED list is the same as in Case One:


• One EPM 3720 Meter for monitoring power

• One Multilin SR745 Transformer Management Relay

• One Multilin SR469 Motor Management Relay



The list of communication protocols in Table 1 shows that all the IEDs communicate on Modbus; because no commnet IEDs are being used, no Modbus Concentrators are needed. However, because the PMCS will be operating on Ethernet, he will need to use an Ethernet Gateway to relay communications between the host and the Modbus networks. Table 1 also indicates that the Modbus IEDs

EPM 3720


600'

Multilin 269+

Motor Relay

Terminating

Resistors

Assembly Line Area

PLC 90/30



550'

Figure 25. Floor layout for Case Three.

Next, Bill checks Table 2 for the Modbus wiring rules and

Table 3 for the Ethernet wiring rules.

He notes that he must properly terminate the RS-485 network at each end and that he must keep his total RS-

485 cable length under 4000 feet, unless he invests in RS-

485 repeaters or puts the IEDs on separate RS-485 networks, which may run in different directions and effectively increase his range.

His cabling limits are satisfied, so Bill selects Modbus addresses for the IEDs, and records them for future

reference. His address chart is shown in Table 10.

29



IED Type

Multilin 565

Multilin 269+

PLC 90/30

EPM 3720

Multilin SR745

Multilin SR469

Physical Location

Power Intake Area

Assembly Line

Assembly Line

Machining

Lathe Area

Milling

RS-485 Port,

Modbus Address

1, 01

2, 01

3, 01

3, 02

4, 01

4, 02

Table 10. IED Addresses for Case Three.

Bill next checks Chapter 3 for physical wiring requirements and rules. He finds that he’ll have to use

Belden 3074F cable for the RS-485 wiring. He also locates the correct terminating resistors at each end of the RS-485 network.

He installs the IEDs according to the instructions in each user manual. He makes communication connections to the RS-485 communication cable in daisy-chain fashion, one IED to the next, with terminating resistors at the final

IED and the host (Ethernet Gateway). While wiring, he follows the RS-485 cable shield wiring rules explained in

Section 2–4 (rule 4).

Bill then assigns local Modbus addresses to the IEDs and sets communication speeds and parameters according to the instructions in each user manual.

He installs the PMCS software at the host PC and configures the IED addresses to match the addresses set at the IEDs.


If any difficulties are encountered, he refers to the troubleshooting guide in Chapter 4.

Case Four

In Case Four, GHO Corp. wishes to create a power management system that will interconnect with their existing corporate Ethernet. They would like the capabilities of both Modbus and commnet IEDs and plan to integrate three separate facilities using repeaters. GHO

Corp. plant engineer Bill has been given the task of designing and installing this system.

As in the previous cases, Bill’s first task is to choose a platform on which the PMCS host will reside. GHO Corp.

requires Ethernet integration, so the flowchart in Section

1-1 determines that the PMCS will reside on Ethernet, requiring an Ethernet Gateway.

Next, Bill makes a list of the IEDs that GHO Corp. wishes to support on their PMCS network. His IED list is:


• Two EPM 3720 Meters and one EPM 7700 for monitoring power



• Six Enhanced MicroVersaTrip trip units

• Three POWER LEADER Meters (with waveform capture)

• One POWER LEADER EPM

• One POWER LEADER MDP Overcurrent Relay


Bill knows that he will need an Ethernet Gateway to connect his Modbus network(s) to Ethernet and both RS-

485 and POWER LEADER Repeaters to reach the remote locations in Facility Two and Facility Three. He checks his

IED list against the list of communication protocols in

Table 1 and notes that some of the IEDs communicate on

Modbus and some on commnet, so he will also need at least one Modbus Concentrator to support communications with the commnet IEDs. The Modbus

IEDs do not all communicate at the same speed, so more than one RS-485 network is required.

Next, Bill checks Tables 2 through 4 for the Modbus,

Ethernet and commnet wiring rules.

The EPM 7700, being a native Ethernet device, can be connected directly to the Ethernet hub Bill intends to install near his office. He’ll connect the hub to the corporate LAN, to his PC, to the 7700, and finally to the

Ethernet Gateway. Bill, realizing the LAN is shared by the entire building, installs an Ethernet data line surge

30


Chapter 2 – Network Design protector at the hub on the incoming line from the EPM

7700 IED to shield the rest of the network from potentially damaging transients.

Because he has only six Modbus IEDs (five IEDs and the

Modbus Concentrator) and 12 commnet IEDs to connect, he requires only one RS-485 network (each RS-485 network accommodates up to 31 Modbus IEDs and up to

215 commnet IEDs). However, because his Modbus IEDs communicate at several different baud rates, Bill decides to assign them to different RS-485 networks to achieve greater system performance.

He also notes that each RS-485 network must be properly terminated at each end. He must keep the RS-485 cable length of each RS-485 network under 4000 feet, unless he uses RS-485 repeaters, as on Network 3, to span the 3,500 feet to Facility 2.

The commnet rules are also easy to comply with. Each of the commnet segments must be kept under 1000 feet, unless repeaters are used to extend the range of the segments, as is required to reach the commnet IEDs in

Facility 3. Each commnet segment is limited to four commnet IEDs, and no segment may have more than one waveform capture meter (POWER LEADER Meter). Bill makes sure that his POWER LEADER Meters are limited to one per segment.

Bill now turns to his floor layout, to see just where the wiring could be run and how much distance it must cover.

He maps where his IEDs must be located and where the host PC will sit. He then measures the cable runs required to connect the IEDs to the host PC, keeping in mind that the RS-485 rules require him to daisy-chain the Modbus

IEDs one after another from the Ethernet Gateway and the commnet IEDs (four per segment) from the Modbus

Concentrator. His floor layout is shown in Figure 26.

The RS-485 cabling is less than 4000 feet for each of the

RS-485 networks, except for Network 3, where RS-485 repeaters are used to bridge the 3,500 feet to Facility Two.

Each of the commnet segments requires less than 1000 feet of cable, except for segment three, where POWER

LEADER Repeaters are used to span the 5000 feet to

Facility Three. The wiring rules are satisfied.

Bill selects Modbus addresses for the Modbus IEDs and

Modbus equivalent addresses for the commnet IEDs, using the worksheets in the back of the Modbus Concentrator User

Guide

(GEH-6491), and records them for future reference.

Bill’s address chart, found in Table 11, follows the floor

layout.

Ethernet connection to corporate LAN

Bill's Office

Ethernet

Ethernet

Hub

100'

Ethernet connection to EPM 7700 is surge-protected

Ethernet

Ethernet

Gateway

RS-485 networks terminated at Ethernet Gateway

Lathe Area

650'

EPM 7700

Milling Area

Network 1 -

9600 baud


600'

EPM 3720

Multilin 565


Network 2 -

2400 baud

Machining Area

600'

Multilin 269

Assembly

Line

Area

EPM 3720

PLC 90/30


550'

Long-range

RS485 cable run

3500 feet

Facility Two

RS485 repeater

Terminating

Resistor

Terminating

Resistor

Facility Three

POW ER

LEADER

Meter

EMVT

RS485 repeater

ECM

POWER

LEADER

Repeater

Long-range commnet cable run

5000 feet

Commnet Segment 1

PLEPM EMVT

Segment 2

EMVT EMVT

Modbus

Concentrator

Segment 5

EMVT EMVT

Segment 4

POWER

LEADER

Meter

MDP

Segment 3

POWER LEADER Repeater

POWER LEADER

Meter

Figure 26. Floor layout for Case Four.

31



IED Type Physical Location

Multilin 565

Multilin 269+

EPM 7700

PLC 90/30

Modbus Concentrator

EPM 3720

EPM 3720







POWER LEADER Meter

POWER LEADER Meter

POWER LEADER Meter

Power intake area

Assembly line

Lathe area

Assembly line

Facility 2, north wall

Machining

Milling










POWER LEADER EPM Facility 2, Segment 1

POWER LEADER MDP Overcurrent Relay Facility 2, Segment 4

Spectra ECM Facility 3, Segment 3

RS-485 Port, Modbus

(or equivalent) Address

Port 1, IED 01

Port 2, IED 01

N/A - native Ethernet IED

Port 3, IED 02

Port 3, IED 03

Port 4, IED 01

Port 4, IED 02

Port 3, IED 33

Port 3, IED 40

Port 3, IED 41

Port 3, IED 50

Port 3, IED 70

Port 3, IED 71

Port 3, IED 51

Port 3, IED 72

Port 3, IED 60

Port 3, IED 34

Port 3, IED 61

Port 3, IED 52

Table 11. IED Addresses for Case Four.

Chapter 3 provides physical wiring requirements and rules. For commnet wiring, he’ll use Belden M8719 cable.

For RS-485 wiring, he’ll use Belden 3074F cable and the correct terminating resistors for both ends of the RS-485 networks.

Bill installs the IEDs at the equipment according to the instructions in each user manual and runs the RS-485 cable for each RS-485 network from the Ethernet Gateway to each Modbus IED in daisy-chain fashion, one IED to the next, and terminated at each end.

Bill runs the commnet cable from the Modbus

Concentrator for each commnet segment, grounded only at the Modbus Concentrator.

He assigns local Modbus addresses to the Modbus IEDs and sets communication speeds and parameters according to the instructions in each user manual.

Next, Bill sets the local address at each commnet IED according to what he wants the Modbus-equivalent address of each IED to be. He configures the Modbus

Concentrator, either manually or with the autoconfigure option, following the instructions in the Concentrator

User Manual. During configuration, the Concentrator probes each of its commnet segments for IEDs, records their commnet addresses, and assigns a Modbus-equivalent address so that communication from the PMCS will be directed to the correct IED.

Bill configures the Ethernet Gateway, assigning a unique

IP network address after he checks with the LAN administrator to determine which IP addresses are available. He then sets the serial port communication parameters for each Gateway port after referring to document GEH-6505, Ethernet Gateway User’s Guide, for information on configuring the Gateway serial ports.

Bill assigns a unique IP address to the EPM 7700 meter’s

Xpress Card based on information in the EPM 7700 user documentation and the addresses he received from the

LAN administrator.

He installs the PMCS software at the host PC and configures the IED addresses in the DDE server. Next, Bill modifies the 7700 network configuration file for the EPM

32



7700, according to the GE 7700 Gateway User’s Guide (DEH-

40035).

When all connections have been made and the IEDs and software are appropriately configured, Bill applies power to the system and runs tests to assure that everything is functioning properly. If any difficulties are encountered, he refers to the trouble-shooting guide in Chapter 4.

Case Five

In this case study, the circumstances are similar to those in

Case One, with the addition of several RS-485 dual-port

IEDs. The PMCS host resides on Modbus, connected to several RS-485 Modbus segments.

The IED list is:

• One EPM 7300 Electronic Power Meter

• One Multilin SR745 Transformer Management Relay

• One Multilin SR760 Feeder Management Relay

• One Multilin 269+ Motor Relay

• One Multilin 565 Feeder Management Relay

• Two dual-port RS-485 Modbus Monitors to serve as remote-viewing stations for the IEDs on segments 3 and 4

• One Modbus Concentrator to support the commnet

IEDs below

• One POWER LEADER Electronic Power Meter


• One Enhanced MicroVersaTrip-C trip unit

He checks the list of communication protocols in Table 1 and notes that most of his IEDs communicate on Modbus, but because he wants to use several commnet IEDs in the

Machining area, he’ll need a Modbus Concentrator. As well, the Modbus IEDs communicate at different baud rates, and Bill makes a note that they should be placed on separate RS-485 networks for improved performance. He decides to use four RS-485 networks supported by the recommended communications card at the host PC.

Bill now turns to his floor layout to see just where the wiring could be run and how many feet of cable will be needed. He maps where his IEDs must be located and where the host PC will sit. Next he measures the cable runs required to connect the IEDs to the host PC, keeping in mind that the wiring rules require him to daisy-chain the

IEDs on each RS-485 network one after another.

Bill calculates the cable length of each RS-485 network and finds that none are over the 4000-foot limit, so he won’t need to use any RS-485 repeaters. The commnet segments are also within the wiring limits, so no POWER LEADER

Repeaters are required.

The factory floor is very large though, and Bill wants to be able to view IED data at several locations to save walking all the way back to his office every time he wants to check an

IED. To serve this purpose, he’s purchased a pair of dualport Modbus Monitors, which he will install in the Milling and the Machining areas, respectively. He checks the

Modbus Monitor wiring rules and sees that he’ll be able to connect RS-485 Network 3 to the RS-485 Port A of each

Monitor and RS-485 Network 4 to the RS-485 Port B of each Monitor. This will allow him to view data from the

IEDs in these areas at either station as well as back in his office at the host PC.

Proper termination is required at each end of the network and is provided at the RS-485 card by placing jumpers between the correct pins (see RS-485 card user manual).

The appropriate terminating resistors must be used at the opposite end of each RS-485 network, per Section 2–4, rule

4.

The network architecture diagram Bill creates is shown in

Figure 27.

RS-485 networks terminated at host PC

Bill's Office

100'


550'

Lathe Area

SR750


350'

Milling Area


Multilin 565

400'


600'

Assembly Line Area

Multilin 269+

Motor Relay

Terminating

Resistors

SR469

Motor

Management

Relay

300'

Multilin 239

Motor Protection

Relay

RS-485

Port A

RS-485

Port B

Modbus Monitor #1

550'

750'

Machining

Area

300'

Modbus

300'

Concentrator

RS-485

Port A

RS-485

Port B

Modbus Monitor #2

EPM 3720

Electronic

Power Meter

400'

Spectra ECM

EMVT-C

Trip Unit

250'

250'

50'

POW ER LEADER EPM


Figure 27. Floor layout for Case Five.

Confident that his new design will provide maximum performance and with his wiring requirements and limits

33


Chapter 2 – Network Design met, Bill selects Modbus addresses for the IEDs. He checks

Section 2-7 and sees that he can assign the Modbus IEDs on each network any Modbus address between 1 and 247

(except for the Modbus Concentrator, which must have an address between 1 and 32). The commnet IEDs must have

Modbus-equivalent addresses between 33 and 247. He selects addresses and records them for future reference.

The address chart is shown in Table 12.

RS-485

Network #

1

3

3

3

4

4

4

4

4

4

4

4

2

3

IED Type Physical

Location

Multilin 565

Multilin 269+

SR469 Motor

Management

Relay

Modbus Monitor

#1, RS-485 Port A

Multilin 239

Motor Protection

Relay

Modbus Monitor

#2, RS-485 Port A

Power intake area

Assembly line

Assembly line

Lathe area

Machining area

Machining

Multilin SR750

Feeder

Management

Relay

EPM 3720

Milling area

Modbus Monitor

#1, RS-485 Port B

Milling area

Lathe area

Modbus Monitor

#2, RS-485 Port B

Modbus

Concentrator

Machining area

Machining area

EMVT-C trip unit Machining area

Spectra ECM

POWER

LEADER EPM

Machining area

Machining area

Table 12. IED Addresses for Case Five.

Modbus

Address

01

01

01

02

03

04

01

02

03

04

05

33

34

35 to the next, terminated at both ends of each RS-485 network, double-checking his wiring against the example provided in Section 2–4. Since several of his Multilin IEDs have two ports, he is careful to connect only one RS-485 port per IED. The Modbus Monitors are also RS-485 dualport, but Bill carefully follows the wiring instructions to correctly connect them to the RS-485 networks. The A port of each Monitor is connected to one RS-485 network and the B port of each is connected to another network.

He must also bear in mind proper shield-grounding considerations: each RS-485 IED grounded at only one point and no two IEDs’ grounds connected (Rule 4,

Section 2-4). The Multilin 565 special grounding considerations are also taken into account (see Chapters 2 and 3).

Bill assigns a Modbus address to each IED. He then sets communication speeds and functional and protective parameters according to the instructions in each user manual.

Bill installs the PMCS software at the host PC and configures IED addresses at the host to match the addresses assigned to each IED on the network.

Configuration files for the Modbus Monitors are downloaded to the units or created using the Monitor’s

“Create from PMCS” feature (see DEH-027 for details).



Chapter 3 provides Bill with physical wiring requirements and rules. He’ll use Belden 3074F cable, readily available.

He also locates the correct terminating resistors at both ends of each RS-485 network.

He installs the IEDs according to the instructions in each

IED’s user manual. He then makes connections to the RS-

485 communications cable in daisy-chain fashion, one IED

34



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35

Chapter 2 – Network Design. ABB POWER LEADER PMCS Network Architecture

Chapter 2 – Network Design

2–1 Modbus Rules

2–2 Ethernet Configuration Rules

Table 3. Ethernet configuration rules2–3 Ethernet

Network Considerations

2–4 Commnet Configuration Rules

2–5 Modbus Wiring Rules – Diagrams

2–6 Commnet Wiring Rules – Diagrams

2–7 Performance Recommendations

2–8 Addressing the IEDs

2–9 Multiple RS-485 Networks – Addressing

2–10 System Expansion

2–11 Case Studies

Related manuals

Table of contents

Chapter 2 &ndash; Network Design. ABB POWER LEADER PMCS Network Architecture