transformer

Transformer

Transformer is a kind of electrical device that can change the potential/voltage or current electrical power.

A transformer works on the principle that energy can be transferred by magnetic induction from one set of coils to another set by means of a varying magnetic flux. The magnetic flux is produced by an AC source. The coil of a transformer that is energized from an AC source is called the primary winding (coil), and the coil that delivers this AC to the load is called the secondary winding (coil).

               

In TJB Power Plant, the output from generator have voltage in 22,8 KV and using the transformer change into 525 KV follow the Jawa-Bali grid voltage. Others output from this generator is also change into 10KV for own plant consumption and 550V for generator excitation.

-         type of transformer

There are three kind of transformer type, which are:

1. Power transformer that use for change the electrical power
2. Instrumentation transformer, use for supply instrument device. This type consists of current transformer and voltage transformer.
3. Control transformer for support the system.

This picture showed the construction of the generator transformer that changes voltage 22,8KV from generator to be 525KV.

-         condition monitoring and maintenance

o       Benefits

a.       Expanded operation time

b.      Reduced life cycle costs

c.       Increased reliability

o       Actions

a.       periodical oil samples, like of breakdown voltage, dissolved gas analysis (DGA), extensive oil analysis (once in every 10 yrs)

b.      periodical visual inspections, like of integrity of transformer, gauges, relays, filters etc., infrared monitoring (every 2 yrs)

c.       scheduled overhauls:

§         Minor overhaul (3...6 yrs) checking on-load tap changers, oil filtering and vacuum treatment, relays and auxiliary devices

§         Major overhaul checking once in technical life-time, cleaning, tightening and drying

§         Chemical analyses checking analysis of insulation paper (once in 10 yrs)

§         Electrical tests

Critical part from transformer that required condition monitoring:

•         On-load tap changer

•         Bushings

•         Insulations

•         Gaskets

•         Oil filtering system

•         Protective equipment

–        valves

–        relays

–        meters and indicators

Equipment Failure Analysis

Procedure for equipment failure analysis consists of:

1. gather information
2. Inspection and Testing
3. Assessments including :

Ø      Analyze

Ø      Summarize finding

4. Corrective Action
5. Reporting
6. Follow up

Unit interlocks diagram logic:

Unit will tripped at condition

• UT A Differential (87 UTA)
• UT A Over current (50/51 UTA)
• UT A LV Neutral Over Current (51 UTNA)
• UT A Fault
• UT A OLTC Protection
• UT B Differential (87 UTB)
• UT B Over current (50/51 UTB)
• UT B LV Neutral Over Current (51 UTNB)
• UT B Fault
• UT B OLTC Protection

Two Unit Operations

Case 1

Case 2

Unit Transformer Protection System
This protection system covers the 22.8/10.5kV Transformers.
When this protection system detects the fault in Unit 1A, the system outputs
the signal to the lockout relay 86UTA1, consequently the following circuit
breakers and equipment will be tripped by 86UTA1 operation.

• 525kV Circuit Breaker “1TJ4” and “1TJ14”
• 22.8kV GMCB 1
• FCB41E1
• 10kV Unit Boards Incoming Circuit Breakers “52UB IA” and “52UB 1B”
• Boiler 1
• Steam Turbine 1

When this protection system detects the fault for Unit 1B, the system outputs
the signal to the lockout relay 86UTB 1, consequently the following circuit breakers and equipment will be tripped by 86UTB1 operation.

• 525kV Circuit Breaker “1TJ4” & “1TJ14”
• 22.8kVGMCB 1
• FCB 41E1
• 10kV Unit Boards Incoming Circuit Breakers “52UB1A” and “52UB1B”
• Boiler 1
• Steam Turbine 1

When this protection system detects the fault for Unit 2A, the system outputs the signal to the lockout relay 86UTA2, consequently the following circuit breakers and equipment will be tripped by 86UTA2 operation.

• 525kV Circuit Breaker “2TJ4” and “2TJ14”
• 22,8kV GMCB 2
• FCB 41E2
• 10kV Unit Boards Incoming Circuit Breaker “52UB2A” and “52UB2B”
• Boiler 2
• Steam Turbine 2

When this protection system detects the fault in Unit 2B, the system outputs the signal to the lockout relay 86UTB2, consequently the following circuit breakers and equipment will be tripped by 86UTB2 operation.

·        525kV Circuit Breaker “2TJ4” and “2TJ14”

·        22.8kV GMCB 2

·        FCB 41E2

·        10kV Unit Boards Incoming Circuit Breaker “52UB2A” and “52UB2B”

·        Boiler 2

·        Steam Turbine 2