BE1-951
General Information
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SECTION 1 • GENERAL INFORMATION
DESCRIPTION
The BE1-951 Overcurrent Protection System is an economical, microprocessor based, multifunction system
that is available in a drawout, H1 (half-rack) or S1 package. BE1-951 features include:
Directional Three-Phase Overcurrent Protection
Directional Ground Overcurrent Protection
Directional Negative Sequence Overcurrent Protection
Directional Power Protection
Control Protection
Breaker Failure Protection
Automatic Reclosing
Voltage Protection
Frequency Protection
Breaker Monitoring
Metering Functions
Communication
BE1-951 relays have four programmable contact sensing inputs, five programmable outputs, and one alarm
output. Outputs can be assigned to perform protection, control, or indicator operations through logical
programming. For example, protection functions could be programmed to cause a protective trip. Control
functions could be programmed to cause a manual trip, manual close, or automatic reclose. Indicators could
be configured to annunciate relay failure, a settings group change, and others.
Protection scheme designers may select from a number of pre-programmed logic schemes that perform the
most common protection and control requirements. Alternately, a custom scheme can be created using
BESTlogic.
A simplified "How To Get Started" procedure for BE1-951 users is provided in Section 2,
Quick Start.
FEATURES
The BE1-951 relay includes many features for the protection, monitoring, and control of power system
equipment. These features include protection and control functions, metering functions, and reporting and
alarm functions. A highly flexible programmable logic system called BESTlogic allows the user to apply the
available functions with complete flexibility and customize the system to meet the requirements of the
protected power system. Programmable I/O, extensive communication features, and an advanced HMI
(Human-Machine Interface) provide easy access to the features provided.
The following information summarizes the capabilities of this multifunction device. Each feature, along with
how to set it up and how to use its outputs, is described in complete detail in the later sections of this
manual.
Input and Output Functions
Input functions consist of Power System Measurement and Contact Sensing Inputs. Programmable Contact
Outputs make up the output functions. Input and Output functions are described in the following paragraphs.
Power System Measurement Functions
Three-phase currents and voltages are digitally sampled and the fundamental is extracted using a Discrete
Fourier Transform (DFT) algorithm.
The voltage sensing circuits automatically configure themselves internally for single-phase, three wire or four
wire voltage transformer circuits. Voltage sensing circuitry provides voltage protection, frequency protection,
and watt/var metering. Neutral (residual) and negative sequence voltage magnitudes are derived from the
three-phase voltages. Digital sampling of the measured frequency provides high accuracy at off-nominal
values.
An auxiliary voltage sensing input provides protection capabilities for over/undervoltage monitoring of the
first and third harmonic of the VT source connected to the Vx input. This capability is useful for ground fault
protection or sync-check functions.
