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Why Current Transformer Placed Between Power Transformer and Breaker in Substation?
Wiki User
∙ 12y ago
A current transformer is primarily used at the neutral point of a transformer for earth fault protection.
A neutral current transformer will measure any ground fault current which will essentially flow from the star point of the transformer.
A fault-detection device other devices is connected to the current transformer and, if the fault current exceeds a certain trigger value, the fault-detection device will give a trip command to an earth-fault relay to disconnect the supply of electricity to the transformer.
Additional Answer
Current Transformers are widely-used in substations to (a) allow the measurement of currents in the high-voltage lines, and (b) to operate protective relays. There are many different types of protective relays, and their function is to disconnect faults by (a) detecting them, and (b) tripping the appropriate circuit breaker(s).
Wiki User
∙ 9y ago
Wiki User
∙ 12y agoIn high-voltage systems, current transformers and voltage transformers (also known as 'potential' transformers) are widely used not just to monitor currents and voltages, but to operate protection system relays. Protection systems are used to disconnect high-voltage equipment in the event of an electrical fault, by tripping any relevant circuit breakers. As there are many different types of protection system, there is no definite answer to your question, but it will be associated with protecting whatever device or circuit the circuit breaker is supplying.
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Type of transformers used in gas insulated substation?
Current transformer and voltage transformer . This transformers are actually measuring instruments which measures the quantity of current and voltage coming out of the substation.
Difference between potential transformer and current trasnformer?
The difference between current transformer and potential transformer is that the secondary of a current transformer can not be open circuited while under service whereas that of the potential transformer an be open circuited without any damage to the transformer.
What usually happens at consumer end when the current carrying capacity of transformer is exceeded?
What should happen is that the circuit-breaker should trip to cut off the current before the transformer becomes damaged by overheating.
What happen when 220v dc is applied to a 220v ac single phase transformer?
The current would rise until it blows the fuse or breaker and that would produce an arc as the transformer's inductance tries to maintain the current.
Why transformer rating is not given in kw?
Transformer rating is based on the maximum temperature a transformer can run at. This temperature is dictated by the amount of current flowing through the transformer windings. This is why transformers are rated in KVA (voltage * current), not kW - it doesn't matter what the phase relationship is between voltage and current, just the magnitude of the current.
Type of transformers used in gas insulated substation?
Current transformer and voltage transformer . This transformers are actually measuring instruments which measures the quantity of current and voltage coming out of the substation.
What is the main function of a current transformer in switchyard substation?
use of CT
Why two trip coil require in breaker?
Transformer is HEART of the substation and Circuit Breaker is the LUNGS of the substation.At faulty condition, large amount of current will flow.so trip function is very important at that timeone coil is faulty means, another one coil will trip the connection to the healthy circuit.
Difference between potential transformer and current trasnformer?
The difference between current transformer and potential transformer is that the secondary of a current transformer can not be open circuited while under service whereas that of the potential transformer an be open circuited without any damage to the transformer.
What usually happens at consumer end when the current carrying capacity of transformer is exceeded?
What should happen is that the circuit-breaker should trip to cut off the current before the transformer becomes damaged by overheating.
What happen when 220v dc is applied to a 220v ac single phase transformer?
The current would rise until it blows the fuse or breaker and that would produce an arc as the transformer's inductance tries to maintain the current.
What size main breaker feeding 480v 75 kva transformer?
An exact breaker size can not be given because the voltage, and hence the calculation for current, is not given. A transformer shall be protected by an over current device that is not rated at more that 150% of the primary current.
Components used to build the substation?
Substation main components include the following:1. The power transformer which is the heart of the Substation. It is the Power transformer that steps up (in the case of a step up Substation for transmission) or steps down (in the case of step down Substation for distribution) the voltage e.g. 132/33kV (step down), 33/132kV (step up).2. The Auxiliary transformer (which is fed from the output of the Power Transformer). This transformer powers the substation accessories and auxiliary equipments such as controls, lighting, Substation control room etc)3. Disconnecting switch or Isolators4. Earthing switch for grounding the main line in case there is need for maintenance work5. Control relays and Protective relays for short circuit, over voltages etc6. Instrument transformers e.g. voltage transformers, current transformers that will take current from the main high voltage line in case of an over current on the line and produce a current that the protective relays can operate with.7. Supervisory Control and Data Acquisition (SCADA) systems for line monitoring and control8. DC power supply system in the form of batteries for supplying DC loads such as emergency lightings, relays, rectifiers, chargers etc.9. Lightning arrestors10. Surge arrestors11. Switchgears for the high and low voltage levels, AC/DC panels12. Circuit breakers for the high and low voltage levels
How do you wire a 277 to 120 volt transformer?
The voltage 277 volts is a three phase line to neutral voltage of a 480 volt system. What is needed for the protection of the transformer is a two pole breaker from the 480 volt CDP (Central Distribution Panel). The breaker will be sized to the KVA of the transformer. The wire will be sized to the breaker plus 25%. The electrical code requires that on motor and transformer feeders, they be sized to 125% of the total current capacity of the equipment.
Why is the live wire not called positive?
Because it is normally carrying alternating current which is alternating between positive and negative at 50 (60 in the US) cycles per second (hertz). Since the other end of the supply transformer is connected to earth at the substation the live wire is "live" with respect to earth. Usually it is used in conjunction with the neutral wire which is really just another earth at the substation.
What is the operation of isolator?
An 'isolation transformer' is a 1:1 ratio mutual transformer. It electrically isolates the secondary circuit from the primary circuit without changing the voltage level. A bathroom shaver socket uses an isolation transformer.
What is the purpose of main switches?
The main breaker limits the overall current to the building. Most buildings have many branch circuits that sum to more current than the service is rated for. This is not a problem as all the branch circuits are not used under high current draws at the same time. The main breaker protects the main wiring in the meter and to the transformer, and the transformer itself, from heavy current loads. It also protects from shorts in the main distribution panel.
