ADR233B
Ref ID : ADR233B/IM/PS
Rev No. : 05
Page No. : 126 of 479
3. W2 Ph CT Secondary 1A/5A
4. W2 Ph CT Primary 10 – 5000A
5. EF CT Secondary 1A/5A
6. EF CT Primary 10 – 5000A
7. CT Star Point Towards Object/Away From Object
8. VT Primary 0.1 – 800 KV in step 0.1kV L-L
9. VT Secondary 110/120V (Line to Line)
The above settings are used to set the Current transformer and potential transformer settings to
establish proper measurements of Power system parameters based on power system condition.
CT Star point is for proper operation differential function.
4.6 Two winding Phase Differential Protection
Two winding Transformer Differential Protection (87T) functions of ADR233B uses the well-
known current differential principle where current entering the protected equipment is compared
with the current leaving the protected equipment. If there is no fault, the current entering the
transformer will be equal to the current leaving the transformer multiplied by the inverse of the
turn’s ratio. If there is a fault in the transformer zone, the currents will not be equal, which results
in a differential current. This differential current is proportional to the fault current for internal
faults, but approaches zero for any other operating conditions. The IED trips the circuit breakers
protecting the transformer when it detects a minimum level of differential current.
The differential scheme creates a well-defined protection zone between the CT sets protecting
the transformer. Any fault within the differential protection zone is called an internal fault, while
any fault outside the differential protection zone is called an external fault. The differential
protection function of ADR233B will be asserted only for internal faults.
In PROTECTION setting menu the “Ph Differential” parameter setting is used to enable or
disable the differential protection function.
Amplitude correction
ADR233B provides automatically amplitude correction based on the reference power rating,
transformer voltage ratings, CT ratios and connection type (star or delta) to scale the secondary
currents to a common base .The mismatch of current transformer ratio is compensated by
software in ADR233B relay.
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