GE Multilin L60, Instruction Manual

Page: 274 / 752

5-144 L60 Line Phase Comparison System GE Multilin
5.5 GROUPED ELEMENTS 5 SETTINGS
5
– 3TL-TR-SPC-2FC: three-terminal line, permissive tripping scheme, single phase comparison, two frequency
channel carrier to two other terminals.
– 3TL-BL-SPC-2FC: three-terminal line, blocking scheme, single phase comparison, two frequency channel carrier
to two other terminals.
– 3TL-TR-DPC-3FC: three-terminal line, permissive tripping scheme, dual phase comparison, three frequency
channel carrier to two other terminals.
– 3TL-BL-SPC-3FC: three-terminal line, blocking scheme, dual phase comparison, three frequency channel carrier
to two other terminals.
A two-frequency channel (2FC) can be either amplitude modulated (AM) on-off carrier or a high-low frequency
shift keying (FSK) system.
In blocking schemes, the open breaker echo element must be disabled. Additional information about phase
comparison can be found in the
Theory of operation chapter.
• 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, mixed I_1+I_2 / K signal, or single 3I_0 signal can be chosen as the
operating signal for the FDH and FDL detectors and positive/negative square pulses generation. The constant K in the
mixed excitation signal is adjustable.
• 87PC MIXED SIGNAL K: Selects the K factor used in the mixed excitation operating signals I_2 – K

I_1 and
I_1+I_2 / K . For the mixed I_1+I_2 / K mode, the setting range is limited from 0.08 to 0.25.
• 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:
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,
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.
REF ANGLE SETTING PHASE ROTATION, ABC PHASE ROTATION, ACB
Carrier in phase A 90° 90°
Carrier in phase B 240° + 90° = 330° 120° + 90° = 210°
Carrier in phase C 120° + 90° = 210° 240° + 90° = 330°
NOTE
NOTE
NOTE