ASB Power Transformers Testing Laboratory I

Introduction:

Laboratory is designed in order to do routine, type and special tests according to standards (except for short-circuit and mechanical withstand test) during the production of transformers that have maximum 250 MVA power and of 400 kV operation voltage.

Dimensions of test area, control room and machine hall of laboratory :

Test area : 15,5 m x 25 m x 18m ( width-length-height )
Control room : 7 x 7 m.
Machine hall : 10 x 6 m. and 6,5 x 8 m
Capacitor banks hall: 22,5 x 4 m

250 MVA, 380 kV transformer during test		350 kV, Separate Source over Voltage Withstand Test System

Building:

Test Area:

Side walls, ceiling and floor are screened as “Faraday Cage” and noise insulation is provided. There is a crane with two crooks (3 tons and 500 kg) for elevation, assembly and disassembly.

Floor:

Structure of the floor is designed according to transformer weights; also surface of square-shaped structure which made of 200 mm “I” profile is covered with 10mm metal sheet. Over the metal sheet, 8 mm epoxy is laid. By this way, it is possible to transport transformers with air cushion.

Earthing:

Many earthing rods (deep earthing) which are made of 6 m length, galvanized pipes, are inserted and joined with galvanized strips, by this way earthing system has been established.

Three terminals at three different places are predicted in order to do earthing connections on the floor during the test. These terminals are connected to earthing rods. Also the metal sheet on the floor is connected to earthing rods too.

To complete Faraday Cage, metallic surface on the walls and ceiling is connected to the metal sheet on the floor.

Cable Channels and Manholes:

Under the test area, cable channels and manholes are predicted for power and control circuit connections of control room and machine halls. (They are made of galvanized steel pipes, placed under faraday cage and connected to earthing system.)

Faraday Cage :

Side wall surfaces and ceiling are made from perforated galvanized metal sheets shaped like trapezoid and welded to each other. Lighting armature’s places on ceiling and glass parts between control room and test area are made of cage wires which include stainless steel wires..

Transport Door :

For entrance and exit of laboratory, vertical moving transport door is made which has 7.5 m width and 12 m height, precautions are taken for screen and noise insulation.

Noise Insulation :

To make noise level measurements of transformers, noise insulation is made on laboratory side walls, ceiling and doors. Noise level is measured minimum 30 dB.in test area.

Lighting, Heating and Ventilation :

At the laboratory test area, average 450 lx lighting level is provided. Lighting is made with sodium-vaporous lamps. Also, incandescent lamps are used once in every group in order to provide fast lighting.

For heating, (noiseless) heaters are placed closer to the floor level which can blow totally 24.000 m3 hot-air per hour.

During the temperature rise test, in order to eject hot-air, low-velocity noiseless absorbent fan system is made on laboratory ceiling which can absorb totally 104.000 m3 hot–air per hour.

Control Room :

Control room is screened separately (Faraday Cage) and connected to the test area screen system. Noise insulation is predicted against outer place.

Test control desk and measuring instruments

Machine Halls :

Machine halls are made in two different places. At first place, boards, rotating machines and compensation reactor is placed, at the second floor transition-transformers are placed and at the upper floor, compensation capacitor and accurate current and voltage transformers are placed.

Motor - Generator and Control Boards

Test Equipment and Measuring Instruments :

Laboratory equipment and measurement devices for transformer tests are arranged as;

• Alternative current test and energy (losses measurement) tests, lightning and switching impulse test equipments
• Measurement and control devices

High resolution impulse measurement and analysis system		Measuring Transformers (CT’s and PT’s) 100 kV, 4000 A.		45 MVAr, 62,5 kV Capacitor Banks

Power Supply and Generators

Power supply of laboratory which is needed during tests and measurements is provided by two ways. One of them is, feeding directly from 34.5 kV network supply, the other is over from the generators. There are 60 Hz, 1000 kVA generator, 50 Hz 330 kVA generator and 150 Hz 500 kVA generator for induced voltage tests in the laboratory

Test Transformers and Reactors

To provide the compatibility between source voltage and test voltage, 4,7 MVA power and 62.5 (84) kV voltage, 3-windings Step-Up transformer is used. Also, in order to increase 60 Hz generator output to 34.5 kV, a 2000 kVA Step-Up transformer is built.

For induced voltage test, there are two reactors, 720 kVAr and 1000 kVAr, for compensation of 150 Hz generator.

For Separate Source over Voltage Withstand Test, 150 kVA, 350 kV single-phase transformer and 350 kV capacitive voltage divider are provided.

Compensation

For compensation of 60 Hz generator, 2 types of capacitor groups have been established. The first group has 1000 kVAr adjustable capacitors. The second group has totally 45 MVAr capacitors which can be connected directly to test output; also they are adjustable with variable voltage levels up to 62.5 kV without voltage supply.

Impulse Generator

Voltage of 2000 kV and total power of 200 kJ impulse generator, 2000 kV voltage divider and chopped wave unit exist.

Measuring System : 10 bit, 120 MHz digital measuring system.

Impulse generator, Voltage divider and chopped wave unit..

Measuring Devices

An advanced power (losses) measurement system exists that have totally %0.1 measurement uncertainty. System provides automatic tap changing of precise current and voltage transformers and does measurements with the help of power analyzer.

Partial discharge measurements are made synchronously at 4 channels. Measurement device can do both partial discharges (PD) and RIV measurements. Measurements can be done as small band and wide band. Partial discharge diagnostic patterns (PRPD) and its frequency spectrum analyses can be determined

During partial discharge measurement, 75 kV, 50 A filters are serial connected to supply circuit.

Laboratory partial discharge background noise level is less than 10 pC.

Laboratory Performance

Best ASB I Laboratory is designed in order to do routine, type and special tests (except for short-circuit withstand test) of transformers that have maximum 400 kV operation voltage and maximum 300 MVA power, according to standards.

Laboratory Single Line Diagram