Product Description; Introduction; Overview - GE B30 Instruction Manual

2 PRODUCT DESCRIPTION

2 PRODUCT DESCRIPTION 2.1INTRODUCTION
The B30 Bus Differential System is a microprocessor based relay that provides protection and metering for a busbar with
up to six feeders. Protection is provided by a low impedance percent differential element with features that make it immune
to CT saturation. Both biased (restrained) and unbiased (unrestrained) differential protection functions are provided.
A dynamic busbar replica mechanism is provided by associating the breaker and switch status signals with the differential
zone currents.
The biased bus differential function operates using both the differential and current directional comparison protection princi-
ples. The differential element uses a dual-slope dual-breakpoint characteristic with the restraining current formed as a max-
imum of the input currents for better stability during through-fault conditions and faster operation on internal faults. The
current directional comparison principle checks the angular relationship between the currents.
The biased bus differential protection operates in the two-out-of-two mode for low differential currents. This improves stabil-
ity during CT saturation conditions caused by comparatively low currents combined with unfavorable phenomena such as
multiple auto-reclose actions. For high differential currents, the bus differential element operates using the differential char-
acteristic alone if CT saturation is not detected. Upon CT saturation detection, the relay switches to the two-out-of-two
operating mode for better through fault stability.
The B30 typical operating time is about 12 ms for fast form-C output contacts and internal usage by user-programmable
logic, and about 15 ms for trip-rated form-A output contacts.
A CT failure alarm function that monitors the level of the differential current is provided. A situation when the differential cur-
rent stays above a pre-defined level for a pre-defined period of time is declared as a CT trouble event, and an alarm is
raised. To prevent false tripping due to CT trouble, undervoltage supervision or an external check zone can be used.
Voltage and current metering is built into the relay as a standard feature. Current parameters are available as total wave-
form RMS magnitude, or as fundamental frequency only RMS magnitude and angle (phasor).
Diagnostic features include an event recorder capable of storing 1024 time-tagged events and oscillography capable of
storing up to 64 records with programmable trigger, content and sampling rate.The internal clock used for time-tagging can
be synchronized with an IRIG-B signal or via the SNTP protocol over the Ethernet port. This precise time stamping allows
the sequence of events to be determined throughout the system. Events can also be programmed (via FlexLogic™ equa-
tions) to trigger oscillography data capture which may be set to record the measured parameters before and after the event
for viewing on a personal computer (PC). These tools significantly reduce troubleshooting time and simplify report genera-
tion in the event of a system fault.
A faceplate RS232 port may be used to connect to a PC for the programming of settings and the monitoring of actual val-
ues. A variety of communications modules are available. Two rear RS485 ports allow independent access by operating and
engineering staff. All serial ports use the Modbus
with baud rates up to 115.2 kbps. The RS232 port has a fixed baud rate of 19.2 kbps. Optional communications modules
include a 10Base-F Ethernet interface which can be used to provide fast, reliable communications in noisy environments.
Another option provides two 10Base-F fiber optic ports for redundancy. The Ethernet port supports IEC 61850, Modbus
TCP, and TFTP protocols, and allows access to the relay via any standard web browser (B30 web pages). The IEC 60870-
5-104 protocol is supported on the Ethernet port. DNP 3.0 and IEC 60870-5-104 cannot be enabled at the same time.
The B30 IEDs use flash memory technology which allows field upgrading as new features are added. The following Single
line diagram illustrates the relay functionality using ANSI (American National Standards Institute) device numbers.
Table 2–1: ANSI DEVICE NUMBERS AND FUNCTIONS
DEVICE FUNCTION
NUMBER
27P Phase undervoltage
50BF Breaker failure
50G Ground instantaneous overcurrent
50N Neutral instantaneous overcurrent
50P Phase instantaneous overcurrent
50_2 Negative-sequence instantaneous overcurrent
50/74 CT trouble
50/87 Unrestrained bus differential
GE Multilin
®
RTU protocol. The RS485 ports may be connected to system computers
DEVICE
NUMBER
51G
51N
51P
51_2
59N
59X
87B
B30 Bus Differential System

2.1 INTRODUCTION

FUNCTION
Ground time overcurrent
Neutral time overcurrent
Phase time overcurrent
Negative-sequence time overcurrent
Neutral overvoltage
Auxiliary overvoltage
Restrained bus differential

2.1.1 OVERVIEW

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