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What is standby earth fault protection And how it is to be coordinated with transformer primary overcurrent relayin DYn11 tf?
Wiki User
∙ 14y ago
DYn 11 is a Delta HV winding and star lv with theneutral brought out. At primary substations it is usual to have a neutral ct. The ct is a last line of defence operating a standby earth fault relay which opens the lv circuit breaker (11kV). It may have a stage 2 setting in case the lv breaker fails to open which opens the hV side. If there is no local hV breaker it may operate a fault throw switch. This device shorts one phase directly to earth forcing the protection at the remote end to operate.
Wiki User
∙ 14y ago
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What size maximum level of primary-only overcurrent protection is required for a 600-volt transformer with a primary current rating of 54 amperes?
100
Why does the primary side of a step down transformer burn out and not the secondary of a 480V to 240V transformer?
Sounds like the wrong size fuse protection was used. The transformer should be protected to its kva capacity.
When would you use current transformer?
A 'current transformer' (CT) is classified as an instrument transformer, which means it is used to provide a small secondary current that is in proportion to its large primary current, for purposes of metering or protection. At the same time, it electrically-isolates the secondary (metering) circuits from the primary circuits (which are often high-voltage circuits) for the purpose of safety.
The incoming voltage from the current source to the transformer is called what?
The incoming voltage from the source to the transformer is called primary voltage.
What is a curect transformer?
A 'current transformer' is a type of transformer which, together with a 'voltage transformer' (or 'potential transformer' in N America), is classified as being an 'instrument transformer'. It is used to reduce large currents to smaller currents which can be measured safely, and to isolate the primary circuit from the secondary circuit for the purposes of safety. Current transformers are also used to drive protective relays used in high-voltage protection systems.
What size maximum level of primary-only overcurrent protection is required for a 600-volt transformer with a primary current rating of 54 amperes?
100
How does the standby earth fault scheme work?
Restricted earth fault protection is used to protect a specific zone, and should not trip for a fault outside of that zone (usually limited to a transformer, and possibly extending to lowside, highside, and tertiary breakers). Stand by earth fault protection is a term I am not very familiar with, but I believe this would be protection that is meant for a specific zone as backup, and can operate for faults outside of this zone. An example might be a highside time overcurrent relay set looking into a transformer, where the transformer is protected by a differential (primary protection), and there is a lowside feeder with relays (primary protection). The highside overcurrent acts as a backup (secondary protection) for the transformer and the feeder, and is delayed due to the nature of a time overcurrent relay.
Why differential relay is not used for 11kv transformers?
It depends what you mean by an '11-kV transformer'; do you mean a primary transformer (33/11-kV transformer) or a distribution transformer (11-kV/400-230-V transformer). Differential protection IS offered on primary transformers.
What is differential transformer protection?
The current input (primary) to a transformer is proportional to the output (secondary) current. Differential protection relays monitor these via current transformers (CT). The percentage of difference between primary and secondary can be adjusted. If it is over the seting the relay will trip the primaryand secondary feeder breakers. Thus indicating an inbalance between internal phasewindings and or shorts to earth.
Why does the primary side of a step down transformer burn out and not the secondary of a 480V to 240V transformer?
Sounds like the wrong size fuse protection was used. The transformer should be protected to its kva capacity.
Does the secondary feeder of a transformer need to be rated at less than the main breaker of the feeder supply panel?
It depends on the situation and how you are utilizing the transformer. Under certain conditions the secondary does not need to be protected. The protection on the primary is enough to protect the secondary side of the transformer.
When would you use current transformer?
A 'current transformer' (CT) is classified as an instrument transformer, which means it is used to provide a small secondary current that is in proportion to its large primary current, for purposes of metering or protection. At the same time, it electrically-isolates the secondary (metering) circuits from the primary circuits (which are often high-voltage circuits) for the purpose of safety.
Why you uluminium on primary side of transformer?
This isn't the case. You can have aluminium or copper on primary or secondary side of a transformer.
How current transfomer is step up voltage transformer n step down current transformer?
Current transformers are not voltage transformers. Current transformer are used for metering or protection purposes, with single turn primary. Generally the secondary current is either 1Amps or 5Amps.
The incoming voltage from the current source to the transformer is called what?
The incoming voltage from the source to the transformer is called primary voltage.
What are the advantages of instrument transformer?
'Instrument transformer' is the collective name for current transformers (CTs) and voltage (or 'potential') transformers (VTs/PTs). These transformers have two functions:to reduce the current or voltage in a high-voltage primary circuit to values that may be measured using regular ammeters or voltmeters ('burdens'), or to provide the current or voltage inputs to protection relays.to electrically-isolate their secondary burdens from the high-voltage primary circuit for the purpose of safety.
What is a curect transformer?
A 'current transformer' is a type of transformer which, together with a 'voltage transformer' (or 'potential transformer' in N America), is classified as being an 'instrument transformer'. It is used to reduce large currents to smaller currents which can be measured safely, and to isolate the primary circuit from the secondary circuit for the purposes of safety. Current transformers are also used to drive protective relays used in high-voltage protection systems.
