Mains pro 1.6.1 Global Guide
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5 Introduction of Application
Guide
5.3 Typical applications of MainsPro protection relay
5.1 Purpose of this manual
The Application Guide serves for the designers and engineers, who process the necessary documentation and
implementation procedures on the installation site, where MainsPro is installed. It contains detailed description
of MainsPro functionalities its practical application.
5.2 MainsPro typical usage
MainsPro is a mains protective relay protecting operation of parallel-to-mains generators or other electrical
resources of distributed generation of electricity. The main purpose is to prevent unwanted interaction between
the generator and mains in case of its abnormal state (e.g. mains failure):
Specific situations may occur, causing e.g. the utility network to momentarily disconnect part of the network
and connect it back by automatic-recloser. During this fault-clearing period, the generators may move away
from synchronism and their eventual re-connection may cause severe damage to the property of the
generator operator, or to the utility equipment.
The sole operation of a generator into an unintentionally islanded part of electricity network provides
potentially dangerous situation. The load of the area may exceed the generator capacity and cause
instability of the voltage, delivered to the consumers connected in the islanded area.
Severe hazards may occur to the working personnel on the grid equipment in the area, where the mains is
presumed as failed, but there are still generators delivering power into this area without central control of
their operation.
These are some of the situations, leading the utilities to strictly require that any parallel connection to the mains
is approved and protection devices with required protective features are installed.
5.3 Typical applications of MainsPro protection
relay
These are installations of any sources of electrical energy. For example:
Cogeneration
Peak-lopping power stations
Stand-by generators with soft return/short-time parallel operation with mains
Microturbines
