Product - GE B30 Instruction Manual

B30 Bus Differential System
Chapter 2: Product description
Product description
This chapter outlines the product, order codes, and specifications.
2.1 Product description
The B30 Bus Differential System is part of the Universal Relay (UR) series of products. It 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 current transformer (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
principles. The differential element uses a dual-slope dual-breakpoint characteristic with the restraining current formed as
a maximum 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
stability 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 characteristic 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
current 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 are built into the relay as standard features. Current parameters are available as total
waveform root mean square (RMS) magnitude, or as fundamental frequency only RMS magnitude and angle (phasor).
B30 devices equipped with CT and VT inputs measure power values.
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, using the Simple Network Time Protocol (SNTP) over the Ethernet port, or using
the Precision Time Protocol (PTP). This precise time stamping allows the sequence of events to be determined throughout
B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 2-1