IEEE Power & Energy Magazine - May/June 2014 - 78

automatic. in contrast, the automatic ras system automates
the entire process of determining, verifying, validating, and
downloading the arming patterns to all ras schemes within
a balancing authority.
This article presents an automatic rasa system within
Bc hydro's fully integrated energy management and ras
system, as shown in figure 2. The focus of the discussion
will be on its functionality in the energy management system (eMs). as a decision-making agent, the arming system
determines the rasa patterns and downloads them automatically to ras schemes at arming stations. The system
has been in real-time operation for years to provide timely
rasa patterns to ras schemes so as to closely match constantly changing power system conditions.
in the British columbia (Bc) power grid, as depicted in
figure 3, the long transmission lines between generation and
load may result in transient and voltage stability problems
under conditions of heavy load and/or major power equipment
outages. ras schemes are extensively used to enhance system stability and mitigate thermal
overloading after contingencies in
Bc hydro systems. an overview
System Disturbances
of Bc hydro's power grid and its
management and control systems is
given later in this article.
Predisturbance
Postdisturbance
in Bc hydro's control centers,
Power Systems
Power Systems
an eMs application that performs
transient stability analysis by pattern matching (TsaPM) is used
Actions
for security assessment and control
of the transmission network. one
Off-Line Decision Process for
of TsaPM's important tasks is to
RAS Arming Pattern
Decision Process for
Determination and Downloading
Inputs
determine the rasa pattern periRAS Actions
Manually the Patterns to RAS
odically (every 4 min) to maintain
RAS Systems
Schemes at Arming Stations
power system security and calculate
transfer limits. conventionally, sysfigure 1. A functional diagram of conventional RAS systems.
tem control center (scc) operators
had to verify, validate, and manually download the rasa patterns
to arming station remote terminal
System Disturbances
units (rTUs) and programmable
Predisturbance Power
logic controllers (Plcs) every 4 min
Postdisturbance Power
Systems
Systems
on a continual basis. given that
operator responses may be slow
and inconsistent in setting up,
Actions
verifying, validating, and downAutomatic Process for RAS
loading rasa patterns to match
Decision Process for
Arming Pattern Determination
rapid changes in power system
Inputs
RAS Actions
and Downloading (from
conditions, a fast, automatic arm(Arming Stations)
System Control Center)
ing process was implemented to
minimize human intervention in
Centralized RAS Arming System
Multiple Distributed RAS Schemes
the routine arming process for
RAS System
ras schemes. This arming system
is fully automatic and only requires
minor human intervention under
figure 2. A functional diagram of an automatic RAS system.

to maintain system reliability. such action may include
changes in demand, generation (MW and Mvar), or system
configuration to maintain system stability, acceptable voltage, or power flows."
in this article, we will zoom out from an individual ras
scheme to look at the overall ras system, which involves
multiple ras schemes and a systemwide ras arming
(rasa) system. We will focus our discussion on the automatic real-time process, from the rasa decision (or recommendation) to actual ras actions in response to disturbances
of the overall system, where the arming patterns (or arming
statuses) of the ras schemes depend heavily on the state of
the power system before the disturbances.
To illustrate the automatic rasa process, we contrast the
functional diagram of a nonautomatic ras system (figure 1)
with that of an automatic one (figure 2). The nonautomatic
ras system requires operators to verify, validate, and manually download the rasa patterns to ras schemes at arming
stations even though the arming pattern determination may be

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