GE DGP Series, Instruction Manual

Page: 152 / 278

5-
8
DGP Digital Generator Protection System GE Power Management
5.3 MEASURING UNIT TESTS 5 PERIODIC TESTS
5
5.3.5 T8: LOSS OF EXCITATION 40-1
1. Make/record the following Settings:
40
(501) SELV2SUP = DISABLE (0)
40-1
(603) CENTER (Center of Zone 1) = ______ ohms
(604) RADIUS (Radius of Zone 1) = ______ ohms
(605) TL12 (Time Delay) = ______ sec.
2. Loss of Excitation is calculated with the following equation:
(equation 5–4)
V
a
and V
b
are vector-phase voltages, I
a
and I
b
are vector-phase currents, and Z is the corresponding
impedance. If the value of Z falls within the Mho circle of the relay, the test pickup will operate and the test
trip will operate TL12 seconds later.
3. Connect relay as shown in Figure 4–8: STANDARD FUNCTIONAL TEST CONNECTIONS on page 4–26.
4. Set up relay in test mode for the 40-1 function; 40-1 ON will be displayed on the MMI. Using the MMI and
the INFORMATION–VALUES command, verify that EXT VTFF = OPEN.
5. Using a 60 Hz source set the voltage (rms) inputs to:
VA = 35 V
∠
0°
VB = 35 V
∠
–120°
VC = 35 V
∠
–240°.
6. Set the phase current so that the impedance falls within the Mho circle and apply to the relay. The test
pickup relay should operate immediately and TL12 seconds later the test trip relay should operate.
7. Change the phase current so that the impedance falls outside the Mho circle, and apply to the relay. The
test pickup and test trip relays should not operate.
8. Apply DC voltage across DI6 (BE2—BE1). Using the MMI and the INFORMATION–VALUES command,
verify that EXT VTFF = CLOSE.
9. Reapply the above phase current that placed the impedance inside the Mho circle. Verify that the test
pickup operates and the test trip does not operate.
Z
V
a
V
b
–
I
a
I
b
–
------------------- =