Abhi
I m an Engineer
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- Jharkhand, India
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- Electrical & Instrumentation Engineer
Differential Protection Relay for Delta Star Power Transformer
- Thread starter Abhi
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petersonra
Senior Member
- Location
- Northern illinois
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- engineer
I don't know much about this type of protection relay but I found this on the internet. It seemed to explain it pretty well.
www.electricportal.info
Differential Protection Of Transformer- Working Principle, Differential Relay - Electricalsblog
The transformer is the main device of the power system and its reliability is more important. Hence protection must be provided to the transformer. Buchholz
www.electricportal.info
Abhi
I m an Engineer
- Location
- Jharkhand, India
- Occupation
- Electrical & Instrumentation Engineer
I had already read this article, not explained elaborately.I don't know much about this type of protection relay but I found this on the internet. It seemed to explain it pretty well.
Differential Protection Of Transformer- Working Principle, Differential Relay - Electricalsblog
The transformer is the main device of the power system and its reliability is more important. Hence protection must be provided to the transformer. Buchholz
AdrianWint
Senior Member
- Location
- Midlands, UK
A star/delta or delta/star transformer has a phase shift of 30 deg across it. ie. the primary & secondary voltages are not in phase.
The 'old' way of cancelling out this phase shift for a differential protection relay connected across such a transformer was to connect the CTs on the star winding side in delta & the CTs on the delta winding side in star. This method corrects the phase shift across the transformer.
More modern protection relays do this using software.
The 'old' way of cancelling out this phase shift for a differential protection relay connected across such a transformer was to connect the CTs on the star winding side in delta & the CTs on the delta winding side in star. This method corrects the phase shift across the transformer.
More modern protection relays do this using software.
Abhi
I m an Engineer
- Location
- Jharkhand, India
- Occupation
- Electrical & Instrumentation Engineer
How difference in CT current is managed in restraining coil?? How and what is happening there bcoz ct current in LV side will be higher.
AdrianWint
Senior Member
- Location
- Midlands, UK
You still need to chose your CT ratios to be the reverse of your transformer ratios (remembering to account for difference in current due to the delta/star relationship as well as the winding ratio) such that the output of both sets of CTs cancel with normal transformer operation.
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- Wisconsin
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- PE (Retired) - Power Systems
The primary and secondary CT ratios may be different, however their output current will need to be the same.
You are just mirroring the actual currents and then comparing them. If there are no faults or measurement errors, in should equal out.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
You are just mirroring the actual currents and then comparing them. If there are no faults or measurement errors, in should equal out.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
You are just mirroring the actual currents and then comparing them. If there are no faults or measurement errors, in should equal out.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
In the real world measurement errors exist and harmonics do not experience the same phase shifts depending on if they are 0, positive, or negative sequence. CT saturation exists. So in practice other coils in the relay (restraint) shape the response to avoid reacting to errors.
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