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ABSTRACT
Now a day’s everything is depending up on the power. So give the reliable supply to the consumers. In distribution systems one of the major parts is "SUBSTATIONS".
An electrical substation is a subsidiary station of an electricity, Generation, Transmission and distribution systems where the voltage is transformed from high to low or reverse using the transformers .Electric power may flow through several substations between generating plant and consumer and may be changed in different voltage levels .the equipment used in substation are Transformer, Lightening arresters, isolator, bus bar, protective devices, Battery charger, earth switches, earth rods. So for of supply the regular maintenance and checking is necessary from that we conclude weather it is suitable or not for the desired operation.
CHAPTER-1
INTRODUCTION
1.1 What is substation?
An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed high to low or the reverse using transformers. Electric power may flow through several substations between generation plant and consumer, and may be changed in voltage in several steps.

The main equipment used in substation are transformers lighting arresters, Circuit breakers PLCC, isolators, bus bars, protective relays, Battery charger, earth switches, earth rods.
1.2 Classification of substations
Classification of substations based on
(1) Service requirements
(2) Constructional features
1. According to service requirements: According to service requirements substations are classified into:
i. Transformer Substations
ii. Switching Substations
iii. Power factor correction substations
iv. Frequency changer substations
v. Converting substations
vi. Industrial substations
2. According to construction features: According to constructional features substations are classified as;
i. Indoor substations
ii. Outdoor substations
iii. Underground substations
iv. Pole mounted substations
1.3 220/132/33 kv sub-station warangal
There are four incoming feeders named as B.pad-2, RSS-1 (Nagaram), RSS-2.There are six 132 KV incoming feeders connected to 132 KV bus. There are 33 KV out going feeders connected 33KV bus. There are three 220/132 KV power transformers and two 132/33 power transformer
Lighting arrestors is placed at the starting point of every feeder to every phase of the line. Capacitive voltage transformer (CVT) follows the lightning arresters .Wave trap is placed next to the CVT for collecting communication signals at higher frequencies
Earth switch is there to transfer the induced voltage on the line when the isolator is open. Then there is an isolator to open the line under maintenance. There is a current transformer to step down the currents to the lower values for the purpose of protection and metering .Next to CT circuit breaker is placed which functions under fault counditions.Then there is a another isolator.
There is 220 KV bus with large size conductors. The bus is very important in the substation. The incoming feeders are connected to it through the control devices. There is an isolator followed by a high voltage 220 KV circuit breaker. Then 220 KV feeders are connected to primary side of power transformer through an isolatar.There are three power transformers of each 100 MVA, 220/132 KV Size.
The output is taken from the LV side of the transformer and connected to 132 KV bus bar through the protecting devices. From every protecting control device cables are connevted to the control center where the continuous monitoring and controlling is done through and relay panel.
Five outgoing feeders are taken out from the 132 KV bus and transmitted the power at lower voltage to the 132/33 KV substations which are located nearby load center.