Introduction - GE ALPS Instruction Manual

1 PRODUCT DESCRIPTION
1.8 PROTECTION SCHEMES
The six standard protection schemes are described in this section. Functional logic diagrams Figure 1–10: STEP DIS-
TANCE LOGIC DIAGRAM through Figure 1–18: HYBRID LOGIC DIAGRAM show the scheme logic for the protection
schemes using conventional AND/OR combinational logic. The elementary diagrams on pages 1–49 to 1–52 show the
external connections to the ALPS relay system. Note that all of the output relays and input contact converters included in
the ALPS are fully programmable by the user. However, for ease of application, the ALPS relay is shipped with the inputs
and outputs assigned as shown in Figure 1–27: ELEMENTARY DIAGRAM WITH DEFAULT I/O (SINGLE PHASE TRIP-
PING) on page 1–49 and Figure 1–28: ELEMENTARY DIAGRAM WITH DEFAULT I/O (THREE PHASE TRIPPING) on
page 1–50. The programmability of the ALPS is discussed in Chapter 13: XPRESSION BUILDER . Figures 1–11: INTER-
CONNECTION DIAGRAM FOR PUTT/POTT WITH NS40A through 1–17: INTERCONNECTION DIAGRAM FOR BLOCK-
ING SCHEME WITH CS61C on pages 1–25 to 1–32 show typical interconnections between the ALPS and an appropriate
carrier/tone equipment for three pilot schemes:
• BLOCKING with NS40A
• POTT with CS28A
• HYBRID with Unblocking CS61C
Figure 1–10: STEP DISTANCE LOGIC DIAGRAM on page 1–27 is the logic diagram for the Step Distance scheme for the
ALPS single phase and three phase models, respectively. Since this non-pilot scheme overlays the other protection
schemes in the ALPS, it is in essence a part of all of them. The Zone 1 distance functions are set to reach no greater than
90% of the positive-sequence impedance of the protected line. All of the ground-distance functions are provided with self-
compensation so that they see only the positive-sequence impedance to a ground fault when the compensation setting is
properly selected to reflect the difference between the zero-sequence and positive-sequence impedance of the line. This
setting is explained in Chapter 2: CALCULATION OF SETTINGS.
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. If the application permits, a forward-looking third zone can be used to
provide backup protection for adjacent line sections out of the remote bus. If a reverse-looking zone is desired, the Zone 4
functions can be reversed. For some applications it may be desirable to implement both a forward-looking Zone 3 and a for-
ward-looking Zone 4.
The phase-distance functions can be placed in or out of service by specifying a separate setting for each protection zone.
The same is true for the ground-distance functions. Zone 2, Zone 3, and Zone 4 each have two independently set zone tim-
ers. One timer is associated with the phase functions, the other with the ground functions.
GE Power Management ALPS Advanced Line Protection System
1.8 PROTECTION SCHEMES

1.8.1 INTRODUCTION

1.8.2 STEP DISTANCE
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