Acceptance Tests; Electrical Tests - ABB KD-10 Instruction Leaflet

41-490J

11.0 ACCEPTANCE TESTS

KD-10 and KD-11 relays have a very small number
of moving parts which might become inoperative.
Acceptance tests in general consist of:
a. A visual inspection to make sure there are no
loose connections, broken resistors, or broken
resistor wires.
b. An electrical test to make certain that the relay
measures the balance point impedance accu-
rately.

11.1 ELECTRICAL TESTS

An adjustable source of three-phase voltage and an
adjustable single-phase current along with a means
for varying the phase relation between current and
voltage are required for testing the relay. The voltage
source may be either "open delta", "closed delta", or
"wye" connected. However, the relay operates only
on delta quantities since it has no neutral connec-
tion.
Check electrical response of the relay using test con-
nections shown in Figure 25 (page 54). Figure 26
(page 55) features the same connections except
shows the use of additional switches that facilitate
fast switchover from "phase-to-phase" fault mode to
"three-phase" fault mode. Test connections, referred
to in the test procedures, are the same on both draw-
ings. Accuracy of the test results will depend to large
degree on the accuracy of the instrumentation used.
In general, it is advisable to restrict instrument read-
ings to the last 20 percent of the scale. For most ac-
curate phase angle readings use phase-shifter
scale. This method requires calibration of the scale
using accurate wattmeter (at 90°–0 watts and at
°
0 –maximum watts), or an accurate phase angle
meter.
Make sure that correct lead-lag reference is estab-
lished. Once the phase-shifter is calibrated, remove
the wattmeter from the circuit. Make all phase angle
reading from phase-shifter scale. This method elimi-
nates the need for switching the current ranges in
phase angle meter when used and results in superi-
or accuracy. Always observe contact condition be-
fore current is applied. Closed contacts indicate re-
verse voltage sequence applied. Special attention
should be paid to the phase-to-phase fault mode.
Testing may be done outside the case for conve-
nience. All current readings include ±6 percent toler-
ance. This tolerance includes ±2.5 percent factory
12
Type KD-10 and KD-11 Compensator Distance Relay
tolerance and ±3.5 percent allowance for total instru-
mentation error.
All phase angle settings are fault current lagging the
V voltage.
PH1-PH2
The impedance measured by the 3-phase unit in test
1 (Figure 26, page 55) is
ZR
where V is the phase-to-phase voltage and I
L-L
the test current; similarly, in tests 5, 6 & 7 of Figure
26 the phase-to-phase unit measures.
ZR
With phase-shifter set at maximum torque angle
(θ ).
m
(
I 3 phase
test
( Θ Θ
I
test
When testing the 3-phase unit, phase-shifter set-
tings are always set for 30° higher than nominal
maximum torque angle to account for test set-up
where all angle measurements are made with refer-
ence to phase-to-phase and not phase-to-neutral
quantities. The three phase unit maximum torque
angle is always referenced to phase-to-neutral.
At any other angle α, relay reach is
Z = Z
θ
where Z θ = relay reach at maximum torque angle
θ
m.
Test current Iα is calculated as
Iα = ------------------------------- -
I θ
= test current at
m
Equation (19) should be used to predict test current
when plotting impedance circle response of the re-
lay.
The relay is set according to the following chart.
V
L L –
= ---------------- -
1.73I
L
V
L L –
= -------------- -
2I
L
V
L L –
)
= ------------------
1.73Z
R
V
LL
)
– = --------- -
2Z
R
( θ α )
cos
–
m
I
θm
( θ α )
cos
–
m
θ
m
[Equ. 14]
is
L
[Equ. 15]
[Equ. 16]
[Equ. 17]
[Equ. 18]
[Equ. 19]