Functions
2.18 Forward Active Power Supervision (ANSI 32F)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
149
2.18 Forward Active Power Supervision (ANSI 32F)
The machine protection 7UM62 includes an active power supervision which monitors whether the active power
falls below one settable value as well as whether a separate second settable value is exceeded. Each of these
functions can initiate different control functions.
When, for example, with generators operating in parallel, the active power output of one machine becomes so
small that other generators could take over this power, then it is often appropriate to shut down the lightly loaded
machine. The criterion in this case is that the "forwards" power supplied into the network falls below a certain
value.
In many applications it can be desirable to issue a control signal if the active power output rises above a certain
value.
When a fault in a utility network is not cleared within a critical time, the utility network should be split or for ex-
ample, an industrial network decoupled from it. Criteria for decoupling, in addition to power flow direction, are
undervoltage, overcurrent and frequency. As a result, the 7UM62 can also be used for network decoupling.
2.18.1 Functional Description
Active Power Measuring
Depending on the application either slow high-precision measurement (averaging 16 cycles) or high-speed
measurement (without averaging) may be selected. High-speed measurement is particularly suitable for
network decoupling.
The device calculates the active power from the positive sequence systems of the generator currents and volt-
ages. The computed value is compared with the set values. Each of the forward active power stages can be
blocked individually via binary inputs. In addition the entire active power monitoring can be blocked per binary
input.
The following figure shows the logic diagram for the forward active power supervision.
Figure 2-60 Logic Diagram of the Forward Active Power Supervision
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