IEEE Power & Energy Magazine - March/April 2018 - 51

After the installation of this system, cePcO has been
able to properly operate its generation dispatching control
even with the large amount of PV penetration. Optimizing generation unit operation is one of the most important
missions for the cdcc because it has a large financial and
reliability impact on cePcO. If cePcO overestimates the
area demand, unnecessary generation units would operate
(costing several million u.s. dollars per day, a significant
negative financial impact). If cePcO underestimates area
demand, generation capacity shortages and potential blackouts could result. cePcO has been continuously improving
the estimation accuracy of this forecast system by reviewing
the algorithm model that considers three-dimensional geospatial data and snowfall impact.

Development of a New Protection
and Control System
generally, the stability of phase angle and frequency performance worsens for heavily loaded transmission networks, which
may be exposed to transmission contingencies that cause cascading wide-area blackouts. however, restricting the power flow
sacrifices economic dispatch operation. to solve these issues
simultaneously, cePcO implemented the online transient and
frequency stability control system, as shown in figure 4.
traditional transient stability control (tsc) and frequency
stability control (fsc) systems were installed independently

more than 20 years ago. however, the cePcO t&d network
situation drastically changed with the recent large penetration of ders and an increase of nationwide cross-regional
power interchanges.
to cope with these changes, cePcO developed a new protection and control system (Pcs) to prevent cascading widearea blackouts under severe transmission faults. cePcO
named this system Integrated stability control (Isc), which
can realize tsc and fsc functions as a unified system, adapt
to the large penetration of ders, and increase power interchange among different t&d supply areas, nationwide and
across regions.
the Isc system comprises Isc-P (processing), Isc-c
(control), Isc-s (sensing), and Isc-t (transfer trip) components. Isc-Ps utilize high-performance electronic computers
made by two different manufacturers (hitachi and toshiba),
and Isc-c/s/ts use the latest protection relay equipment built
by Mitsubishi. figure 5 shows a diagram of the Isc system.
In the tsc function, Isc-P reads online data from remote
terminal units (rtus), executes detailed transient (angle)
stability simulations, and sends simulation results to Isc-c.
Isc-s sends fault detection data from protection relays
and real-time power flow conditions to Isc-c. Isc-c sends
control signals to Isc-t, utilizing simulation results from
Isc-P and fault detection and real-time power flow from
Isc-s. Isc-t executes load and generator shedding when it

Load

Load
PV
Generator

Main
Network

Isolated System
System Interconnected After Fault Cleared

System Separated After Fault Cleared

TSC: Transient Stability Control Function

FSC: Frequency Stability Control Function

Gen > Load

Rotational
Speed of Gen

Frequency

Without Control

Without
Control

Gen < Load
Frequency
With Control
Without
Control

With Control
With Control
Gen Tripping
Fault Occurred

Gen Tripping
Time

Fault Occurred

Time

Load Shedding
Fault Occurred

Time

figure 4. The CEPCO TSC and FSC system.
march/april 2018

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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2018