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Power Management Control System
Preface
How Does PMCS Work?
The PMCS software runs on a PC (called the host). The host is linked to the power management IEDs through a network (RS-485), and speaks to them using the Modbus
RTU communications protocol
. The heart of PMCS is a piece of software called the PMCS Network and IED
Configurator. The Network and IED Configurator is a
Dynamic Data Exchange Server (we’ll refer to it as the
PMCS DDE Server or simply the Server). It responds to requests for data from other software packages called clients. When the PMCS DDE Server receives a request for data from a client, it sends a message out to the appropriate IED requesting the data. Each piece of data is called a tag. The PMCS DDE Server polls the appropriate tags (or blocks of tags) from each IED and passes the data back to the client which requested it. The Server then begins to monitor that tag; if it changes, the Server notifies the client that had previously requested the data; thus, not only is the current request answered, but the client is also kept informed of later changes.
Some power management IEDs are relatively simple and keep track of only a few power characteristics or events; they require only a few tags at the DDE Server. More sophisticated IEDs keep track of many more pieces of information, requiring a greater portion of the DDE
Server’s resources.
The limit on the number of IEDs that can be managed by the PMCS varies from network to network and is a function of the kind and sophistication of the IEDs that the DDE
Server is tracking. Obviously, the more sophisticated the
IEDs and the greater the demands they place on the DDE
Server, the fewer IEDs that may be managed.
The host is networked to the power management IEDs in one of two fashions. The host may be based directly on the
RS-485 platform and communicate with the RS-485 networks via interface cards. Alternatively, the host may reside on an Ethernet network, talking directly to
Ethernet-capable IEDs such as the EPM 7700, and to
Modbus-native devices via a separate Modbus-to-Ethernet converter which supports the RS-485 networks. This is described in greater detail later in the manual.
Using This Guide
This manual is a simple and direct guide to designing and connecting a power management system based on GE’s
Power Management Control System. Please read the entire manual before attempting to put it into practice.
Chapter 1 provides a basic overview of the PMCS: typical systems and intelligent electronic devices (IEDs) supported. It is imperative that you have a thorough understanding of what the PMCS is and its various components before you read the rest of this book.
Chapter 2 discusses the rules and requirements for designing the network on paper: how far apart IEDs may be located, addressing the IEDs, limits on the number of
IEDs. Chapter 2 also provides several case studies as examples of how to design a PMCS network that will fit your needs. After studying this chapter and the case studies, you should understand how to lay out networks based on PMCS.
Chapter 3 explains the details of actual network construction: types of wire required, termination resistors, how to wire IEDs together. Actual connection details are given in the user manuals of each individual IED, which you should refer to directly.
Chapter 4 offers information on operations and troubleshooting. The information provided here will help you get your system up and running and keep it that way!
Several Appendices offer more detailed descriptions of
PMCS-compatible IEDs and a list of reference publications.
1
EPM 7700 devices are the exception; instead of using Modbus, they communicate directly over Ethernet.
2
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