GE Industrial Solutions POWER LEADER PMCS Network Architecture Guide - Manual (Page 12)

Power Management Control System
Preface
2
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
1 . 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.
1 EPM 7700 devices are the exception; instead of using Modbus, they
communicate directly over Ethernet.
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 trouble-
shooting. 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.