Testing The Differential Element 87T - Siemens 7UT51 Instruction Manual

7UT51 v3
16.3.4 Testing the Differential
Element 87T
Connect your current source to IA primary (as seen in
Figure 16.7).
Note: Any CT input may be used.
Figure 16.7 Differential Setpoint Testing
When testing with the operational parameters, it
should be noted that the setting value 87T refers to the
rated current of the transformer. The pickup values
can change with single and two-phase testing
depending on the vector group of the protected
transformer; this corresponds to conventional circuitry,
when currents are applied via matching current
transformers. Table 16.3 shows these changes as a
correction factor CF depending on the vector group
and the type of fault, for three-phase transformers.
To obtain the trip value, the setting value 87T
(Address 1603) must be multiplied by the CF as
follows:
×
I = I
trip NsecW1
where
I =Nominal current (secondary) of Winding
NsecW1
1
CF =Correction Factor (from Table 16.3)
PRIM-2330C
×
CF Diff-Setting
Ramp up the single-phase current (60 Hz) slowly from
0 A and stop when Trip Contact 1 closes. Ramp the
single-phase current down slowly, from the trip value,
and stop when Trip Contact 1 opens.
Winding 1
(A, B, C)
Type of Fault
Voltage
-
(high side)
-
3 Phase 1.0
-
2 Phase 1.0
1
-
1 Phase 1.5
-
with I Elim.
0
2
-
1 Phase 1.0
-
without I Elim.
0
1 -
I Process is I ELIMINATION, at Address 1106, 1126, or
0 0
1146.
-
2 I Process is either I CORRECTION or WITHOUT, at
0 0
Address 1106, 1126, or 1146.
I is Zero Sequence Current
0
Table 16.3 Operating Current Correction Factor
Expected Results
The relay should trip and LEDs 1 and 2 should light
within +/- 5% of the operating current level, I
that the 87 delay setting is 0 seconds (the default
setting)
For the example values in Table 16.2:
45,000 kVA
--------------------------------------------------------- -
I =
trip
× ×
3 138 kV
The reset value should be approximately 70% of the
pickup test current.
Contacts, LEDs, and LCD
For the default settings, all trip contacts should close,
Signal Relays 1 and 2 should operate, and LEDs 1
and 2 should light when 87 trips. At dropout, the
contacts should reset but the LEDs should remain lit
because they are set to latch. When the current is
turned off, the LCD should display "87Diff GenFlt" and
"87DiffGenTrip."1.
Bench Testing
Secondary Secondary
(a, b, c) or (a, b, c) or
Tertiary Tertiary
(a', b', c') (a', b', c')
Even Num Odd Num
Vector Grp Vector Grp
1.0 1.0
1.0 ~ 0.866
1.5 ~1.73
1.0 ~1.73
Note
trip.
× ×
1 0.2 = 0.63 A
( 300 5 ⁄ )
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