Medium Voltage Substation-1

                       In industries of cement, oil&gas, they have motors, transformer to cater its load. This motors & transformers have rated voltage of 6.6kv to 11kv. For that, they need 6.6kv or 11kv indoor substation which is called MV substation. The term Medium Voltage As per IEV - 601-01-28, is commonly used for distribution system with voltage above 1kV and generally applied upto 33kv. They are built as indoor substation. It is possible because of compact circuit breakers.

SLD of MV Substation

Common Analogy used in substation:-

1. INCOMER:- It is a source of power. It energize bus. It comes from either transformer or another substation. In 6.6kv incomer and outgoing, Vacumn circuit breaker is used, Whereas in 415V LT Incomers and outgoing, Air circuit breakers used.
2. BUSCOUPLER:- As name says it is used to couple two buses. Same rating circuit breaker is used to couple both bus which is used in incomer.
3. LINE PT:- It is used to measure (Check) wheather your incomer is charge from another substation or not. It is a potential transformer which is rated at 6.6kV/110V and it feed to meters and relays.
4. BUS PT:- Simple Potential transformer used to measure bus voltage. It has rating of 6.6kV / 110V.

There is also some scheme.

1. Both incomer cannot ON simultaneously when buscoupler is also ON.
2. Generally in normal condition, Both incomers are in ON condition and Buscoupler is in OFF  position. When one incomer trip then buscoupler will automatically ON.

Some common 415V LT panel names:-

• PCC - POWER CONTROL CENTER:- You can control feeder from here.
• MCC - MOTOR CONTROL CENTER:- You can control motor from here.
• PMCC - POWER CUM MOTOR CONTROL CENTER:- You can control motor as well as feeder from here.

Basic Structure of 6.6 kv panel.

6.6kv Panel

              Above Compartment is for relay and control section. It include various part which is as below.

1. Protective Relay:- For protection purpose.
2. Meters:- For Measurement of Voltage, Current and Power
3. Annunciators:- For indication, at which fault breaker tripped.
4. TNC Switch:- To Close and open the breaker electrically.
5. Local & Remote Switch:- To Close the breaker from locally or remotely.
6. LED Indicators:- To know status of breaker wheaher it is Close or Open.
7. Test Blocks for relay testing
8. Hooter

           Refer above SLD you can see two transformer (TR - 1 & TR - 2) both have same rating of 6.6kV / 415V feed to LT busbar. One transformer can carry whole load of 415V bus but For reliablity and maintanance purpose, two transformers are typically employed at the substation.

MV Substation

                   As shown in above image, Right side panel is 6.6kV HT panel and left side panel is PCC 415V LT Panel. There is a coordination between HT and LT Panel...