ABB HCB-1, Instruction Leaflet

Page: 7 / 28

Type HCB-1 Pilot Wire Relay System 41-971.3M
7
(I
A2
is the phase A negative sequence current):
But:
So:
Equ. (6)
For T = 4
I
S
= 0.5
4.2. NOMINAL PICKUP (All Relays)
The nominal pickup, I
nom
, is defined as
Equ. (7)
Where I
nom
= total internal fault current
K = number of relays (2 or 3)
I
S
= single-relay pickup with pilot
wire disconnected (see above)
0.2 T .2 I
A 1
– .46 I
A 2
4.9 I
A 0
+ + =
I
A 1
0.2
T
5.2
----------- I
A 2
I
A 0
= = =
I
S
I
A 1
I
A 2
I
A 0
+ = =
= 3 I
A 1
0.2 T
( )
3
( )
I
S
3 I
A 1
0.2 T 3
× ( )
5.2
------------------------- 0.12 T (A-G Fault) = = =
I
nom
KI
S
=
For example, in the previous example or a phase-A-
ground fault, the single-relay pickup was determined
as I
S
= 0.5 ampere for 4CH taps with the pilot-wire
open. For a two-terminal line, the nominal pickup for
a phase-A-to-ground fault (4CH taps) is:
4.3. MINIMUM TRIP (All Relays)
With equal inputs to all relays and zero pilot-wire
shunt capacitance, the relays will operate at their
nominal pickup point. The minimum trip points will
vary somewhat from nominal value, depending on
the pilot-wire constants and the magnitude and
phase angle of the various relay input currents. For
example, Figure 6 shows the relay operating points
for a two-terminal line, assuming input current one
relay only.
An example of the characteristics with various cur-
rent distributions shown in Figure 6. The filter output
voltage, V
F
, of each relay, as defined by equation (1)
must be in phase or 180 degrees out-of-phase, in
order for Figure 7 to apply.
4.4. INSULATING TRANSFORMER
Unless otherwise noted, all characteristics presented
include an insulating transformer with each relay.
Two ratios are available: 4/1 and 6/1. The high volt-
age side (H1-H4 Terminals) is connected to the pilot-
wires.
I
nom
A to G
( )
0.5 0.5 2
×
1.0 ampere = = =
Sub 4
183A61
Figure 4. Simplified External Schematic of the HCB-1 Relay System