Schweitzer Engineering Laboratories SEL-787 - Table 4.4 Differential Element Settings; Figure 4.5 Differential Element Harmonic Blocking Logic

4.10
SEL-787 Relay Instruction Manual Date Code 20081022
Protection and Logic Functions
Basic Protection
second and forth harmonic in the operate current. Common blocking prevents
all restrained elements (87Rn) from tripping if any blocking element is picked
up.
However, an independent blocking is used for the fifth harmonic current. In
this logic, an individual element will only disable tripping of that element.
An additional alarm function for fifth harmonic to warn of overexcitation (not
shown in Figure 4.5) employs a separate threshold (TH5P) and an adjustable
timer (TH5D). This threshold and timer may be useful for transformer
applications in or near generating stations.
Figure 4.5 Differential Element Harmonic Blocking Logic
Relay Word bits 87R and 87U are high-speed elements that must trip all
breakers. The factory default assigns 87R and 87U to trip variable setting
TRXFMR. If either bit asserts, this variable asserts bit TRIPXFMR, which
drives contact OUT103. OUT103 connects to an 86 lockout device, which
trips all breakers via multiple sets of contacts.
87HB
_
+
_
+
_
+
5HB2
87R1
87BL1
87R2
87BL2
87R3
87BL3
2_4HBL
2_4HB1
5HB3
2_4HB2
2_4HB3
5HB1
5th
Harmonic
Blocking
4th
Harmonic
Blocking
2nd
Harmonic
Blocking
HBLK=Y
(setting)
I1H2
I1H4
I1H5
IOP1
Relay
Word
Bits
Relay
Word
Bits
Relay
Word
Bits
Relay
Word
Bit
Table 4.4 Differential Element Settings
Setting Prompt Setting Range
Setting Name :=
Factory Defa ul t
XFMR DIFF ENABLE Y, N E87 := Y
WDG1 CURR TAP 0.50–31.00 A
a
a
Range shown for I
NOM
= 5 A; Range for I
NOM
= 1 A is 0.10–6.20 A.
TAP1 := 2.09
WDG2 CURR TAP 0.50–31.00 A
a
TAP2 := 2.09
OPERATE CURR LVL 0.10–1.00 TAP O87P := 0.30
DIFF CURR AL LVL OFF, 0.05–1.00 TAP A87P := 0.15
DIFF CURR AL DLY 1.0–120.0 s A87D := 5.0
RESTRAINT SLOPE1 5–90 % SLP1 := 25
RESTRAINT SLOPE2 5–90 % SLP2 := 70
RES SLOPE1 LIMIT 1.0–20.0 TAP IRS1 := 3.0
UNRES CURR LVL 1.0–20.0 TAP U87P := 10.0
2ND HARM BLOCK OFF, 5–100 % PCT2 := 15
4TH HARM BLOCK OFF, 5–100 % PCT4 := 15
5TH HARM BLOCK OFF, 5–100 % PCT5 := 35
5TH HARM AL LVL OFF, 0.02–3.20 TAP TH5P := OFF
5TH HARM AL DLY 0.0–120.0 s TH5D := 1.0
HARMONIC RESTRNT Y, N HRSTR := Y
HARMONIC BLOCK Y, N HBLK := N