Product Description; Introduction; Overview - GE L30 Instruction Manual

2 PRODUCT DESCRIPTION

2 PRODUCT DESCRIPTION 2.1INTRODUCTION
The L30 Line Current Differential System is a digital current differential relay system with an integral communications chan-
nel interface.
The L30 is intended to provide complete protection for transmission lines of any voltage level. Both three phase and single
phase tripping schemes are available. Models of the L30 are available for application on both two and three terminal lines.
The L30 uses per phase differential at 64 kbps transmitting two phaselets per cycle. The current differential scheme is
based on innovative patented techniques developed by GE. The L30 algorithms are based on the Fourier transform–
phaselet approach and an adaptive statistical restraint. The restraint is similar to a traditional percentage differential
scheme, but is adaptive based on relay measurements. When used with a 64 kbps channel, the innovative phaselets
approach yields an operating time of 1.0 to 1.5 cycles (typical). The adaptive statistical restraint approach provides both
more sensitive and more accurate fault sensing. This allows the L30 to detect relatively higher impedance single line to
ground faults that existing systems may not. The basic current differential element operates on current input only. Long
lines with significant capacitance can benefit from charging current compensation if terminal voltage measurements are
applied to the relay. The voltage input is also used for some protection and monitoring features such as directional ele-
ments, fault locator, metering, and distance backup.
The L30 is designed to operate over different communications links with various degrees of noise encountered in power
systems and communications environments. Since correct operation of the relay is completely dependent on data received
from the remote end, special attention must be paid to information validation. The L30 incorporates a high degree of secu-
rity by using a 32-bit CRC (cyclic redundancy code) inter-relay communications packet.
Several options are available for communication. A faceplate RS232 port can be used to connect to a computer for the pro-
gramming of settings and the monitoring of actual values. The RS232 port has a fixed baud rate of 19.2 kbps. The rear
RS485 port allows independent access by operating and engineering staff. It can be connected to system computers with
baud rates up to 115.2 kbps. All serial ports use the Modbus RTU protocol. The IEC 60870-5-103 protocol is supported on
the RS485 interface. IEC 60870-5-103, DNP, and Modbus cannot be enabled simultaneously on this interface. Also only
one of the DNP, IEC 60870-5-103, and IEC 60870-5-104 protocols can be enabled at any time on the relay. When the IEC
60870-5-103 protocol is chosen, the RS485 port has a fixed even parity and the baud rate can be either 9.6 kbps or 19.2
kbps. The 100Base-FX or 100Base-T Ethernet interface provides fast, reliable communications in noisy environments. The
Ethernet port supports IEC 61850, IEC 61850-90-5, Modbus/TCP, and TFTP protocols, PTP (according to IEEE Std. 1588-
2008 or IEC 61588), and allows access to the relay via any standard web browser (L30 web pages). The IEC 60870-5-104
protocol is supported on the Ethernet port. The Ethernet port also supports the Parallel Redundancy Protocol (PRP) of IEC
62439-3 (clause 4, 2012) when purchased as an option.
In addition to current differential protection, the relay provides multiple backup protection for phase and ground faults. For
overcurrent protection, the time overcurrent curves may be selected from a selection of standard curve shapes or a custom
FlexCurve™ for optimum co-ordination.
The L30 incorporates charging current compensation for applications on very long transmission lines without loss of sensi-
tivity. The line capacitive current is removed from the terminal phasors.
For breaker-and-a-half or ring applications, the L30 design provides secure operation during external faults with possible
CT saturation.
Voltage, current, and power metering is built into the relay as a standard feature. Current parameters are available as total
waveform RMS magnitude, or as fundamental frequency only RMS magnitude and angle (phasor).
Settings and actual values can be accessed from the front panel or EnerVista software.
The following single line diagram illustrates the relay functionality using American National Standards Institute (ANSI)
device numbers.
Table 2–1: ANSI DEVICE NUMBERS AND FUNCTIONS
DEVICE FUNCTION
NUMBER
25 Synchrocheck
27P Phase undervoltage
27X Auxiliary undervoltage
49 Thermal overload protection
50BF Breaker failure
GE Multilin
DEVICE
NUMBER
51P
51_2
52
59P
59_2
L30 Line Current Differential System

2.1 INTRODUCTION

2.1.1 OVERVIEW

FUNCTION
Phase time overcurrent
Negative-sequence time overcurrent
AC circuit breaker
Phase overvoltage
Negative-sequence overvoltage
2
2-1