Protection Scheme Descriptions; Introduction; Step Distance - GE LPS-O Instruction Manual

1.8 PROTECTION SCHEME DESCRIPTIONS

1 PRODUCT DESCRIPTION
1.8 PROTECTION SCHEME DESCRIPTIONS

1.8.1 INTRODUCTION

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The Step Distance protection scheme for phase protection only is included with the LPS-O. The functional
logic diagram is shown in Figure 1–8: STEP DISTANCE LOGIC DIAGRAM. The elementary diagram in Figure
1–11: ELEMENTARY DIAGRAM on page 1–25 shows the external connections to the LPS-O relay system.
Note that all of the output relays and input contact converters included in the LPS-O are fully programmable by
the user. However, for ease of application, the LPS-O relay is shipped with the inputs and outputs as assigned
in Figure 1–11: ELEMENTARY DIAGRAM on page 1–25. The programmability of the LPS-O is discussed in
Chapter 13: XPRESSION BUILDER.

1.8.2 STEP DISTANCE

Figure 1–8: STEP DISTANCE LOGIC DIAGRAM on page 1–21 is the logic diagram for the Step Distance
scheme. The Zone 1 phase distance functions are set to reach no greater than 90% of the positive-sequence
impedance of the protected line. There can be as many as three time-delayed zones. At a minimum, Zone 2
should be selected to provide protection for the last 10% of the protected line not covered by Zone 1.
The phase-distance functions may be placed in or out of service by specifying a separate setting for each pro-
tection zone. Zones 2, 3, and 4 each have independently set zone timers.
1- LPS-O Line Protection System GE Power Management
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