19-03-2012, 01:55 PM
POWER GRID RESTORATION OPTIMIZATION CONSIDERING GENERATING PLANT ISLANDING SCHEME
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I. INTRODUCTION
Large interconnected power systems may be seriously
affected by severe occurrences that could lead to a
cascade of automatic actions. These types of events may
be the source of an uncontrolled network splitting with
harmful effects on power quality to end-users. In highly
stressed operating conditions, a cascade outage may
eventually conduct to a partial or complete blackout. The
power systems operated by the utilities in developing
countries suffer from a large gap between demand and
generation, inadequate transmission capacity, and
nonuniform location of the load centers and generating
stations.
MAHARASHTRA STATE POWER SYSTEM
The western region of Indian Power Grid consists of
Maharashtra State power system, with highest installed
generating capacity of around 15,000 MW (as on
31/03/2005), along with Gujrat, Madhya Pradesh,
Chattisgad, and Goa. Some private players also play a
power game in hands with state electricity Generation
Company. The wide electrical power grid also supports
the system. The figure below indicates the 400 kV power
system network in Maharashtra State with major
transmission lines. The major hydroelectric power station,
Koyna situated in Western Maharashtra has total installed
capacity of 1960 MW.
ISLANDING SCENARIO
The Islanding scheme is presently in operation in the state
for Mumbai region with Reliance (REL) and Tata (TEC),
the private players. For rest of the Maharashtra State,
generating station wise (or generator wise) islanding may
be a hopeful solution to avoid complete blackout for the
consumers. In this paper the stress is given to the
Islanding which will be helpful not only for the
interruption free power supply to the consumers but also
for the system restoration. This Islanding system is
designed for six different sectors in the Maharashtra State
which are consisting of generation, one sector without
generation, so in this way seven sectors are considered.
The figure below (figure: 3) illustrates the seven sectors
along with existing Islanding i.e. Mumbai with existing
transmission lines.
CASE STUDY
A case study for the Power System Restoration (PSR)
technique, which is mentioned in the paper, was studied
for one model sector. This was considered for Nasik
Thermal Power Station (NTPS) which is near to Nasik
city. This power station is situated in western side (Part B
in figure: 2) in Maharashtra State. NTPS feeds power to
Nasik city and surrounding industrial and rural area via
Grid Control Room (GCR) and Old Control Room (OCR)
substations present in power station premises. The OCR
substation is connected with NTPS stage – I (2X140 MW)
via two 150 MVA generator transformers and also
connected with 220 kV double circuit interstate Nasik –
Navsari (Gujrat State) line.
CONCLUSION AND FUTURE WORK
The main aim of the paper is to put more light on the
understanding of the new concept. This scheme is very
helpful for a big power system as in Maharashtra state. In
normal hierarchy, at the time of grid failure, the power
required to start restoration (generally power for thermal
power plants to run auxiliaries) is demanded from the
states where power is available. This of course includes
money and time matters. This can be avoided by using the
proposed scheme. As mentioned earlier the present
restoration methodologies have time constrains to
implement. So this new scheme will definitely help to
reduce restoration time and save the state from total
blackout.