1-4
ALPS Advanced Line Protection System
GE Power Management
1.2 INTRODUCTION
1 PRODUCT DESCRIPTION
1
1.2 INTRODUCTION
1.2.1 DESCRIPTION
The Advanced Line Protection System (ALPS) is a microprocessor-based digital relay system that uses waveform sam-
pling with appropriate algorithms to provide three phase or single phase tripping schemes for transmission line protection,
fault location, and related features. The models covered by this instruction book are intended for either three phase or sin-
gle phase tripping applications. The relay samples the current and voltage inputs from the power system 64 times per
cycle. Protection algorithms process this sampled data in sets of four, sixteen times per cycle. The ALPS uses advanced
Fourier calculation techniques and adaptive measuring functions to achieve high-speed tripping for severe faults.
The ALPS is packaged in a compact 3 Rack Unit high (one RU = 1.75 Inches) 19-inch rack mount case and is available for
either horizontal or vertical mounting. The case outline and mounting dimensions are shown in Figure 3–2: FRONT AND
REAR VIEW on page 3–2.
All models include a full keypad and a liquid crystal display (LCD) for local access to relay data and settings. In addition, up
to three communication ports are provided for both local and remote access with a PC. Each port may be independently set
for ASCII or GEmodem protocols.
1.2.2 APPLICATION
The models covered by this instruction book are designed to be used on transmission lines of any voltage level, with or
without series capacitor compensation, where either single or three-phase tripping is required. Detailed application consid-
erations are described in this chapter and in Chapter 2: CALCULATION OF SETTINGS.
The ALPS can provide high speed detection and clearing of power system faults, and includes logic for step distance and
five standard pilot tripping schemes. The scheme logic is described in Section 1.8: PROTECTION SCHEMES on page 1–
23. The external connections for the ALPS are shown in the elementary diagrams on pages 1–49 to 1–52.
The ALPS is available with either a contact interface to the pilot channel equipment or an electronic (5 V, 20 mA) interface
so that the relay may be applied with a wide variety of channel equipment. Typical channels include: AM and FSK via power
line carrier (PLC), FSK via microwave, and multiplexed fiber optic cable.
1.2.3 PROTECTION FUNCTIONS
The measurement functions are listed in Table 1–2: ALPS MEASUREMENT FUNCTIONS on page 1–5.
The Zone 1 distance functions provide secure high-speed tripping for all fault types over most of the protected line. The
Zone 1 ground distance functions can be selected to be either ground variable-Mho distance functions, or ground-reac-
tance distance functions. The ALPS also offers ground quadrilateral distance functions as Zone 1 ground distance func-
tions. A unique adaptive reach for the supervising Mho characteristic is used when ground-reactance functions are
selected.
Overreaching Zone 2 phase and ground distance functions are used for pilot tripping schemes. Ground-directional overcur-
rent functions can be selected to replace or supplement the overreaching zone (Zone 2) ground-distance functions in any
of the pilot schemes. The ALPS also offers Zone 2 ground quadrilateral characteristics. The Zone 2 phase and ground dis-
tance functions are provided with independent timers for time delayed backup protection.
Overreaching Zone 3 phase and ground distance functions are provided with independent timers for time delayed backup
protection. The ALPS also has the option for quadrilateral ground-distance functions.
The Zone 4 variable-Mho distance functions can be reversed in direction when a reversed or blocking function is required.
When the POTT2, Blocking or Hybrid scheme is selected, Zone 4 is automatically set to the reverse direction, because
these schemes require a reverse-looking blocking function. The Zone 4 phase and ground distance functions are provided
with independent timers for time delayed backup protection. The ALPS with three phase tripping also has the option to use
Zone 4 ground quadrilateral distance functions for time-delayed backup protection.
When both phase and ground distance functions are used for a zone of protection, six individual measuring functions are
available: three for phase distance and three for ground distance. The algorithm that implements the variable-Mho measur-
ing functions is derived from designs that have evolved through several different families of static analog and digital relay
systems which have accumulated decades of dependable and secure in-service experience.
An instantaneous overcurrent tripping function (50G) provides direct tripping for severe phase-to-ground faults. Time-over-
current tripping (51G) provides time-delayed backup tripping for phase-to-ground faults. Either or both of these ground-
overcurrent functions can be controlled by the NT negative-sequence directional trip unit, at the customer’s discretion.
