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AEP/INEZ Station

UCA2 MMS/Ethernet Project Demonstration

As part of the EPRI sponsored Utility Initiative project, we propose to hold a demonstration at
our Inez Station and site of the Unified Power Flow Controller(UPFC). We have scheduled
, Octo
ber 27th 1999

to demonstrate our use of MMS/Ethernet communications. At
the demonstration, we will emphasize the Inez station LAN and WAN communications with the
remote sites. A short overview on the Utility Initiative history and the UPFC theory of operat
will also be provided. It is proposed that we all meet at a hotel in Ashland, KY the night before
and proceed to Inez station early the next morning at 8:00am. We should arrive at Inez at
approximately 9:30am and tour the station. AEP will have presen
tations, view the HMI screens
and WAN, LAN and PLC equipment and also operate the UPFC and remote equipment via the
WAN/LAN communications. Detailed information concerning the hotel, carpools, etc. will be
provided to those planning to attend. Please conta
ct Jack Robinson at phone# 408

0969, E
mail or John Burger at phone# 614
7220 or E
mail at
for demonstration reservations by our cutoff date of Friday, October 8th.

AEP is one of the largest investor owned electric

utilities in the United States. AEP, in
conjunction with Siemens and EPRI, developed the Unified Power Flow Controller or UPFC. It is
the most advanced of a group of Flexible AC Transmission System (FACTS) devices used to
control the transmission system v
oltage and power flow. The UPFC has the ability to
independently control the real and reactive 138KV transmission power flow on a transmission
line while also regulating the local bus voltage. It allows real
time control and dynamic
compensation of the tra
nsmission system. The UPFC provides for the independent control of the
transmission voltage, phase angle and line impedance, all the elements of the transmission power
flow equation.

The UPFC was installed at AEP’s Inez 138KV station to maximize the utiliz
ation of the existing
area transmission lines and to defer construction of new facilities. To utilize the UPFC as
envisioned requires communications between Inez station, six remote stations, area dispatching
and the corporate office. AEP did not want to c
reate a separate Wide Area Network (WAN)
within the company for this purpose. We wanted to utilize the existing corporate WAN to
transmit the control and monitoring information between Inez and the remote stations. Therefore,
we needed an open protocol tha
t was compatible with the AEP WAN, robust, high speed and
allowing for device interoperability. UCA 2.0 (Ethernet/OSI/MMS) was chosen for the
development of the station LANs and WAN communication system.

The communications system designed includes LANs at
Inez, six regional substations, AEP
headquarters and the area dispatch center. All of the nodes communicate with MMS on the AEP
WAN. Attached is a figure showing the ‘Inez area control and remote access’ as described above.
All remote stations incorporate
the same LAN configuration and architecture as depicted in the
figure titled ‘Inez area Typical Remote Location’. They utilize a flat panel HMI, Modicon PLC
with Ethernet/MMS protocol, communications hub and router. Inez station has a dual LAN

that was required to integrate existing Modbus Plus and Modbus protocols with the
more robust, Ethernet/MMS protocol. The Modbus Plus and Modbus LANs were used to connect
the Siemens UPFC controller and the PLCs used by AEP to control the UPFC. A
ations PLC was used as a gateway between Ethernet/MMS and Modbus Plus.

The communications system was developed to regulate area 138KV transmission line flows and
the bus voltage at Inez station. Three transmission lines are monitored in the area. For exam
ple, if
any of the monitored lines overload, the UPFC will change the power flow at Inez to reduce flow
on these lines. The UPFC will also control six shunt capacitor banks at both Inez and at three
remote stations. When a contingency occurs in the Inez ar
ea, the UPFC can also change its
output, within one cycle, to either inductive or capacitive VARs, to stabilize the area voltage.