BE1-81O/U and BE1-79A/79M — frequency and auto-reclosing relays

Description

BE1-81O/U is a digital frequency relay that protects power systems against underfrequency and overfrequency. The relay supports up to four independent frequency setpoints, which makes stepped automatic underfrequency load shedding possible. Loads are disconnected in portions, so the frequency returns to normal without shutting down the whole network. For each setpoint the overfrequency or underfrequency mode is chosen, its own time delay is set, and a separate LED indicator is provided. The low burden on the VT circuits reduces the cost of voltage transformers.

BE1-79M is a microprocessor multi-shot auto-reclosing relay for circuit breakers. It can be programmed for up to four reclosing attempts, the sequence is selected with jumpers, and the delays are adjusted separately for each attempt. Most faults on lines are brief, so reclosing after a pause often restores supply without staff intervention. A separate fast (pilot) reclosing function is provided for line auto-reclosing. Optional outputs control tripping circuits and block the transformer OLTC during an auto-reclosing cycle.

Optional functions limit the duration of the close command and of the whole cycle. Additional inputs allow blocking of the reset timer and of all timer operations, accepting a signal to switch to lockout, or activating a special sequence. The BE1-79A auto-reclosing relay is also produced.

The BE1-81O/U frequency relay is used for automatic underfrequency load shedding in power systems where frequency falls after loss of generation. The same relay detects overfrequency if the corresponding mode is selected for a setpoint. LED indication shows which setpoint has operated. The BE1-79M works together with the line circuit breaker: after a trip it issues closing commands according to the programmed sequence and, after an unsuccessful reclosing, leaves the breaker open.

All these relays have low burden on the CT and VT circuits, which reduces the requirements for measuring transformers, a power supply with a small load on the battery, a simple setup interface without a computer, and LED signalling. The relay can be tested in its case with test plugs. They are used in distribution networks of utilities, at substations, in industrial power systems and for protecting generating units against frequency deviations.

Technical specifications

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