Functional Description; Introduction; Line Measurement Techniques; Single-Phase-To-Ground Fault - ABB REL 301 Instruction Leaflet

2. 1

INTRODUCTION

Both the REL301/302 relay systems detect faults in three zones of phase and ground distance.
Zones 1 and 2 are forward set, Zone-3 can be set forward or reverse. REL302 has a separate
pilot zone (see Section 2-5).
The R-X Diagram, Figure 2-1, shows a composite of characteristics available with REL301/302.
Zone-1 phase and ground settings are chosen to provide substantial coverage of the protected
line without overreaching the next bus. A setting of 80% of the line impedance is recommended.
Faults occurring within the reach of the Zone-1 measurement cause direct tripping without re-
gard to any action occurring at the remote terminal.
Zone-2 settings are chosen to assure that faults occurring on the next bus are detected. Settings
are chosen (independent of the Zone-1 settings), generally to be 120 to 150% of the line imped-
ance. Any fault occurring on the protected line will be detected by this Zone-2 measurement
(within the fault resistance and current limitations of the relaying system settings). Zone-2 trip-
ping occurs after a time delay of T2 Definite Time or T2 Torque Control Overcurrent Time, de-
pendent on setting choice.
The Zone-3 measurement has a directional setting choice, and may be chosen to respond to
forward or reverse faults. The reverse sensing option is used in conjunction with the T3 time de-
lay, chosen to coordinate with adjacent terminal(s) Zone-2 timing. The forward sensing option
produces time delayed backup to other devices sensing forward faults.
Blinder measurements (B1/B4, B2/B3) are available for out-of-step blocking. The inner blinders
also restrict the trip reach of all of the 3-phase fault measuring units (load restriction).
2. 2

LINE MEASUREMENT TECHNIQUES

Line measurement techniques applied to each zone include:
• Single-Phase-To-Ground fault detection
• 3-Phase fault detection
• Phase-to-Phase fault detection
• Phase-to-Phase-to-Ground fault detection
2.2.1

Single-Phase-to-Ground Fault

Single-phase-to-ground (ØG) fault detection (Figure 2-2) is accomplished by 3 quadrature po-
larized phase units (ph-A, ph-B, ph-C). Equations 1 and 2 are for operating and reference quan-
tity, respectively. The unit will produce output when the operating quantity leads the reference
quantity.
V
–
XG
V
Q
Section 2. FUNCTIONAL DESCRIPTION
Z – Z
  I
0L 1L
I + Z
----------------------- -
 
X 0 CG
Z
1L
I.L. 40-386.4
(1)
(2)
2-1