GE L60 Instruction Manual page 193

5 SETTINGS
3. In blocking schemes, the open breaker echo element must be disabled.
• 87PC BLOCK: Selects a Flexlogic™ operand that blocks operation of the phase comparison scheme (for example, an
operand that indicates operation of a communications channel failure detector).
• 87PC SIGNAL SOURCE: Selects whether current is supplied from one current source (either single-breaker CT appli-
cation or dual-breakers with CTs summed externally) or from two separate sources (breaker-and-a-half or ring configu-
rations), where currents from both CTs are fed into the L60 individually.
87PC SIGNAL: A mixed I_2 – K × I_1 signal or a single 3I_0 signal can be chosen as the operating signal for the FDH
•
and FDL detectors and squaring amplifier. The constant K in the mixed excitation signal is adjustable.
87PC MIXED SIGNAL K: Selects the K factor used in the mixed excitation operating signal I_2 – K × I_1.
•
• 87PC MIXED SIGNAL REF ANGLE: This setting applies exclusively to the negative-sequence mixed mode operating
current ("Mixed I_2-K*I_1") and specifies a leading angular shift for the originally developed operating signal. The oper-
ating signal is always developed taking phase A as reference for calculating symmetrical components. This setting can
be used to control the angular position of the operating current with respect to the voltage of any phase that might be
used by the line carrier in a particular application. This allows minimizing the impact of positive corona on dependability
of single-comparison blocking schemes. Effectively this setting shifts the transmitted pulses in time with the intent to
minimize – for majority of faults – the overlap between the space periods and positive peaks of the voltage in the phase
used by the carrier. Normally, this angle shall be adjusted to follow the conductor used by the carrier plus the extra line
characteristic angle (approximately 90°).
The following setting rule applies particularly for blocking schemes:
REF ANGLE SETTING
Carrier in phase A
Carrier in phase B
Carrier in phase C
Some applications are not concerned with the corona effect, such as when the applied carrier uses narrow-band filter-
ing, or similar techniques improving security and dependability of transmission.
Shifting the angle reference is considered an advanced principle and does not have to be used in all applications. If
used in situations that are not concerned with the corona effect, this setting will not alter operation of the relay: neither
improves it, nor impairs it. The only effect would be in possibly different operating times for different fault types, with the
average times unchanged.
This setting must be set identically at all line terminals or the scheme will be dramatically impacted to the
extent of entirely diminishing security and/or dependability. The same caution applies to the scheme type,
NOTE
operating current, and K settings.
• 87PC FDL PICKUP: This setting is used to select the FDL pickup value. FDL is used as a start-keying element.
• 87PC FDL AUX: This setting assigns an auxiliary element (an impedance element, for example) in parallel with FDL to
start channel keying. This is beneficial for power system conditions when FDL cannot pick up.
• 87PC FDH PICKUP: This setting is used to select FDH pickup value. FDH is used as a trip-arming element.
• 87PC FDH AUX: This setting assigns an auxiliary element (an impedance element, for example) in parallel with FDH
to permit tripping. This is beneficial for power system conditions where FDH cannot pick up.
• 87PC CH1(2) ASYMMETRY: These settings set the symmetry adjustment to make "positive" and "negative" halves of
the power cycle of the received signal from the remote terminal via communication channel noise symmetrical. Refer
to the test procedures for more detailed information.
• 87PC CH1(2) DELAY: These settings delay the local signal until the remote signal is received. Refer to the test proce-
dures for more detailed information.
• 87PC CH1(2) RX VOLT: These settings select a threshold for the signal received from the carrier(s). They are depen-
dent on the carrier nominal output voltage. A value of 10 to 20% of carrier nominal output voltage is recommended.
• 87PC TRIP SECURITY: This setting controls security of the response of the 87PC function on the first and following
coincidence periods. When set to "First Coincidence" the function uses the primary
operates when the integrated value exceeds the setting. Each coincidence period is treated independently. When set
to "Enhanced", the function applies the value for the first coincidence period specified by
GE Multilin
PHASE ROTATION, ABC PHASE ROTATION, ACB
90° 90°
240° + 90° = 330° 120° + 90° = 110°
120° + 90° = 110° 240° + 90° = 330°
L60 Line Phase Comparison Relay
5.5 GROUPED ELEMENTS
setting and
87PC STABILITY ANGLE
87PC ENHANCED STAB ANGLE
5
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