What is Battery bank and Purpose of its use in Industry

What is Battery Bank  ??

Battery bank is one type of series connection of same type of batteries to achieve desired DC voltage as per requirement.

Series connection of Battery

Capacity of battery bank 

Capacity of battery is calculated in terms of Ampere-Hour (AH).

Suppose battery bank capacity is 500 AH and connected load ampere is 25 Amp then battery bank can supply DC power source up to 20 hours with 25 Amp load. 

25 Amp X 20 hours = 500 AH

Purpose of use in Industry

1) Useful in case of AC power supply fails for illumination and emergency pumps running purpose.

2) Useful for control of the plant by controlling machines through computer digital software like DCS and SCADA.

3) Useful for providing power supply to relays for electrical protection  purpose.

4) Useful for providing indication and annunciation purpose.

5) Providing power supply to tripping and closing coil of electrical circuit breakers.

Half yearly, Yearly and interval of 2 year check points for Transformer Maintenance

Checkpoint for interval of 6 months

1) Check transformer oil for acidity (<=0.03 mg KOH/g), sludge content (non detectable), flash point (>=140 degree), Dielectric dissipation factor (tan delta) (<=0.010) , Interfacial tension  (>=35 mN/m) and specific resistance (resistivity) (>=6x10^12 om cm at 90 degree).

OIL ACIDITY TEST

OIL SLUDGE TEST

OIL FLASH POONT TEST

OIL TAN DELTA TEST

OIL INTERFACIAL TEST

Yearly checkpoint of Transformer

1) Check mechanical function of Buchholz relay.

2) Marshalling box to be cleaned from inside. All illumination, space heaters, to be checked whether they are functioning properly or not. Check all the terminal connections of control and relay wiring and tighten.

3) Clean all the relays, alarms and control switches along with their circuit, in R&C panel (Relay and Control Panel) and RTCC (Remote Tap Changer Control Panel) by appropriate cleaning agent.

4) Check pockets for OTI & WTI (Oil Temperature Indicator & Winding Temperature Indicator) on the transformer top cover and replace oil if required.

5) Check proper function of Pressure Release Device.

6) Check insulation resistance and polarization index of transformer with battery operated megger of 5 KV range.

7) Check resistive value of earth connection and rizer with clamp on earth resistance meter.

8) Check DGA (Dissolve Gas Analysis) of transformer Oil annually for higher KV rating transformer and once in 2 years for lower KV rating transformer.

9) Check for proper sealing of marshalling box for cable holes.

10) Check all protections and alarm circuits by actual external initiation with relay operation.

11) Check IR value of cooling motor winding, noise and vibration of fan.

12) Check painting and surface finish.

13) Check tightness of bolts in gasket joints.

Checkpoint for interval of 2 years

1) Check calibration of OTI and WTI.

2) Check tan-delta measurement of bushings of transformer.

3) Check operation of gauge and healthiness of air cell.

Monthly and 3 months checks for Transformer Maintenance

Monthly checkpoint

1) Check oil level in oil cap under silica gel breather. If it is found below the specified level, oil to be top up as per specified level.

2) Check breathing holes in silica gel breather & clean properly if required, for proper breathing action. 

3) Silica gel breather should be of blue colour. If colour is pink then replacement or heating of silica gel is required.

4) Check oil level in buchholz relay.

Checkpoint for interval of 3 months

1) Check for dirt deposition on bushings and tightness of its oil filling plug & examine for any crack in porcelain discs.

2) Check for BDV (>=60 KV) and PPM (<10 PPM)of transformer oil and tap changer oil.

3) Check for cooling fan manual and auto function. Lubricate fan bearings if required.

4) Check step by step mechanism operation & end position limit switches in On load/off load tap changer. Lubricate all bearing points.

Daily checks for Transformer Maintenance

Transformer maintenance is done at regular intervals for trouble free operation and to prevent breakdown of transformer from service.

Below are the daily check points for transformer maintenance.

1) Check oil level of main conservator and OLTC tank. It should be as per specified level.

2) Check for oil leakage from any point of transformer. If leakage is observed, suitable action to be taken for attending oil leakage.

3) Check oil level in bushings. It should be as per specified level.

4) Check oil and winding temperatures whether they are normal or not.

5) Check loading amperes of transformer against rated figures in display of relay or in control room monitor display.