![Schweitzer Engineering Laboratories SEL-321 Instruction Manual Download Page 309](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-321/sel-321_instruction-manual_1216711309.webp)
Date Code 20011026
Maintenance and Testing
7-39
SEL-321/321-1 Instruction Manual
Ground Distance Element Supervisory Conditions
Note:
Unless otherwise indicated, all of the supervisory conditions listed below apply to the
ground mho and ground quadrilateral distance elements.
Phase and Ground Nondirectional Overcurrent Elements, 50Ln and 50Gn
Each zone ground distance element is supervised by two nondirectional overcurrent elements,
50Gn and 50Ln, where n indicates the zone associated with the overcurrent element. For
example, the relay may assert the Zone 3 A-ground distance element only if the A-phase current
is greater than the 50L3 setting and the residual current is greater than the 50G3 setting.
Negative-Sequence Directional Element
The ground distance protection function is supervised by the negative-sequence directional
element to provide improved directional security. Forward-reaching distance elements may not
assert unless the 32QF element is asserted. Reverse-reaching distance elements may not assert
unless the 32QR element is asserted.
Loss-of-Potential Logic
If ELOP = Y, Y1, or Y2 the relay supervises the ground distance element logic using the Internal
Loss-of-Potential condition (ILOP). When ELOP = Y, Y1, or Y2 the relay disables the ground
distance elements when a loss-of-potential is detected, regardless of other signals applied to the
relay. If you test the ground distance elements using low voltage signals, set ELOP = N to
simplify the test.
Single-Pole Open Logic
In single-pole trip applications, the relay cannot properly polarize or operate the ground distance
elements associated with an open breaker pole. The relay Single-Pole Open logic disables the
ground distance element associated with an open breaker pole. For instance, if Pole A is open,
the relay cannot operate the A-G ground mho distance elements. If any single-pole is open, the
relay disables all ground quadrilateral distance elements. To simplify distance element tests,
apply control voltage to any inputs assigned to perform the 52 auxiliary functions, or disable the
Single-Pole Open logic by setting ESPO = N.
Three-Pole Open Logic
If significant pole-scatter occurs when a circuit breaker closes, sensitive ground distance
elements may operate undesirably due to the unbalanced signals applied. The SEL-321 Relay
disables the ground distance elements during Three-Pole Open conditions and for a short,
settable time after the breaker closes. The time is set by the 3POD time delay settings. To
simplify distance element tests, apply control voltage to any inputs assigned to perform the 52
auxiliary functions.
Summary of Contents for SEL-321
Page 4: ......
Page 10: ......
Page 12: ......
Page 162: ......
Page 171: ...Date Code 20011026 Event Reporting 4 9 SEL 321 321 1 Instruction Manual ...
Page 263: ...SEL DIRECTION AND POLARITY CHECK FORM ...
Page 264: ......
Page 265: ...SEL DIRECTION AND POLARITY CHECK FORM ...
Page 266: ......
Page 270: ......
Page 358: ......
Page 360: ......
Page 362: ......
Page 366: ......
Page 370: ......
Page 390: ......