110KV/33KV,132 KV/33 KV Substation Single line diagram # Equipment's Testing & Standard Limits

What is Substation?# Indoor & Outdoor Susbtation,132KV/ 33KV, 110KV/33KV, 33KV/415V Substation-(SLD) Single line Diagram, Testing & Standard limits of Substation components, Classification of Voltage levels
Substation Main Equipments and Its Functions
1) Power Transformer: To step up or step down voltage at the same frequency
2) Lightning Arrester: To discharge lightning & switching over voltages to earth
3) Circuit Breaker: Automatic switching during normal or abnormal condition
4) Current Transformer: To step down the current for measurement / protection
5) Potential Transformer: To step down the voltage for measurement / protection
6) Isolator: Disconnection of circuit under no load condition
7) Earthing Switch: To discharge the voltage on dead lines to earth
8) Bus Section: For connecting Incoming / Outgoing Circuits
9) Capacitor Bank: To Improve the power factor of the system & provide compensation to reactive power absorbed by inductive loads, reduce the over loading of the cables, transmission lines & transformers for the same load to be handled
10) Protective Relay: To sound an alarm or to close the trip circuit of breaker so as to disconnect a component during abnormal conditions (over load, under voltage, unbalanced load, short circuits)
11) Battery Banks: To maintain the D.C. supply continuity during A.C. supply failure for keeping equipment in operation for normal & abnormal conditions
12) Station Transformer: To supply of A.C. power for charging the batteries and provide D.C. control supply for station equipments operations, for Illumination, for spring charging motors of breakers, for cooling system of transformer
Some Common Terms used with meanings
1) ONAN - Oil Natural, Air Natural
2) ONAF - Oil Natural, Air Forced
3) OFAF - Oil Forced, Air Forced
4) WTI - Winding Temperature Indicator
5) OTI - Oil Temperature Indicator
6) PRV - Pressure Relief Valve
7) OSR - Oil Surge Relay
8) OLTC - On Load Tap Changer
9) RTCC - Remote Tap Change Control
10) MOG - Magnetic Oil Level Gauge
11) IDMT - Inverse Definite Minimum Time (For Relay)
12) NO - Normally Open Contact
13) NC - Normally Closed Contact
14) LILO - Loop In Loop Out (Used for defining Substation)
15) CRP - Control Relay Panel
16) TTB - Test Terminal Block
17) ACDB - A.C. Distribution Board
18) DCDB - D.C. Distribution Board
19) MB - Marshalling Box (For Breaker, Transformer control)
20) AVR - Automatic Voltage Control (For Tap Changing on RTCC Panel) 8 Detail description of Each Equipments
Main fixtures of Power Transformer are as below
1 Bucholz Relay
2 Oil Surge Relay
3 Explosion Vent
4 Pressure Relief Valve
5 oil Temperature Indicator
6 Winding Temperature Indicator
7 Conservator
8 Breather
9 Oil level indicator
10 Radiators
11 Bushings
12 Tap Changer
Site Testing of Transformer:
1)Insulation Resistance Test -
a) Between HV & Earth.
b) Between LV & Earth.
c) Between HV & LV by suitable range of megger.
2)Voltage Ratio Test :This test is essential to check the output or the secondary voltage on each tap position. By virtue of this test the problems in the OLTC can be easily detected. 3 Phase, 440 V LT supply is applied to the primary side of the transformer and the output volts at the secondary side for each tap position is measured
3)Magnetic Balance Test - This test is carried out to check the balancing of the induced voltages in the windings & flux distribution. Transformer is kept on normal tap position and 3 Phase, 440 V LT supply is applied to the primary windings
4) Vector Group Test - This test is carried out to check correctness of windings connections. The Phase angle difference arises out of the internal connections of the windings.
5) Magnetizing Current Test :
Apply 3 Phase L.T. voltage to primary windings through ammeters (ma) connected in series of windings and keeping secondary winding open. It would be seen that the current drawn by all the three phases would be same. The current is drawn on account of the magnetizing of the core. (Iron loss) It can also be called as no load current when the transformer is charged with rated primary voltage applied across the primary, keeping secondary open.
6) Short Circuit Current Test - Short circuit test is carried out to check the healthiness of windings. Apply 3 Phase L.T. voltages to primary windings & secondary windings are shorted through ammeters of suitable range. If the readings are equal in all three phases, transformer is supposed to be healthy.
7)Oil Test - The oil is used as insulation between windings & core and between windings & tank. Without oil, the paper insulation of the windings could be punctured early which in turn will result in failure of transformer. The oil facilitates cooling of the windings and magnetic circuits. The oil protects windings and core of transformer from the absorption of moisture. The test on oil is divided into two different categories.