GE L30, Инструкция по эксплуатации

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CHAPTER 5: SETTINGS GROUPED ELEMENTS
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-257
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a sum of all sources configured in the current differential element, to detect system disturbances. If the weak condition
exists at one terminal, the voltage-based disturbance detector measures the changes in three-phase voltages (DVA, DVB,
DVC).
The adaptive level detector operates as follows:
•
When the absolute level increases above 0.12 pu for I_0 or I_2, the adaptive level detector output is active and the
next highest threshold level is increased eight cycles later from 0.12 to 0.24 pu in steps of 0.02 pu. If the level exceeds
0.24 pu, the current adaptive level detector setting remains at 0.24 pu and the output remains active (as well as the
disturbance detector output) when the measured value remains above the current setting.
• When the absolute level is decreasing from 0.24 to 0.12 pu, the lower level is set every eight cycles without the
adaptive level detector active. Note that the 50DD output remains inactive during this change as long as the delta
change is less than 0.04 pu.
The current delta level detectors (DI) detectors are designed to pick up for the 0.04 pu change in I_1, I_2, and I_0 currents.
The DI value is measured by comparing the present value to the value calculated four cycles earlier.
The voltage delta level detectors (DV) are designed to pickup for the 0.1 pu change in any of three-phase voltages and the
old voltage is greater than 0.8 pu. The DV value is measured by comparing the present value to the value calculated four
cycles earlier.
The settings are explained as follows.
DD FUNCTION
— This setting is used to enable/disable the operation of the disturbance detector.
DD NON-CURRENT SUPV
— Selects a FlexLogic operand that activates the output of the disturbance detector upon events
(such as frequency or voltage change) not accompanied by a current change.
DD CONTROL LOGIC
— Used to prevent operation of I_0 and I_2 logic of disturbance detector during conditions such as
single breaker pole being open that leads to unbalanced load current in single-pole tripping schemes. Breaker auxiliary
contact can be used for such a scheme.
DD LOGIC SEAL-IN
— Used to maintain disturbance detector output,
50DD SV
, for such conditions as balanced three-phase
fault and low level time overcurrent fault, whenever the disturbance detector might reset.
50DD SV
is maintained until the
chosen FlexLogic operand resets.
DD SEAL-IN BY 87LG
— Used to seal-in the disturbance detector output,
50DD SV 87LG
, especially for the 87LG element
whenever the
50DD SV
might reset before 87LG time delay elapses.
50DD SV 87LG
is maintained until the
87L DIFF PKP G
operand resets.
DD VOLTAGE SUPV
— Used to enable the voltage-based disturbance detector for such applications as the weak condition
exists at one terminal, where the weak-infeed current is not able to trigger the current-based disturbance detector. The
voltage signals used for this detector are taken from the source assigned with the
CURRENT DIFF SIGNAL SOURCE 1
setting.
DD EVENTS
— This setting can be disabled when the disturbance detector element responds to any current disturbance on
the system that results in filling the events buffer and possible loss of valuable data.