T&D World Magazine

Protection Relays for Secondary Distribution

The SIA relays are designed to protect the secondary transformation and distribution centers of electrical grids. The protection features include protection against instantaneous and inverse time overcurrent (for the phases and the neutral) as well as an external trip support (temperature, pressure, etc.) depending on the model.

The protection functions can be enabled by using both the front panel and the communications link to the SICom program. Combining the settings and IEC curves available allows for precise coordination with other equipment.

One of the features of the SIA-C and SIA-A is the use of the operating current itself for self- powering. This means that maintenance of the transformation and distribution centers is reduced. Neither batteries, chargers, nor any other external power elements are required.
Even more, one advantage over other equipment available on the market facilitates the start-up of installations and the carrying out specific operations in adverse conditions. All models can be powered from an external battery, allowing us to guarantee complete operation of the equipment, including tripping due to any faults that may occur.

Main characteristics

  • The SIA-C is a Dual & Self powered overcurrent protection relay using the operating current through three/5 or /1 standard current transformers fitted on the lines. These transformers are also used to obtain current measurements. The equipment can be occasionally supplied by an external battery.
  • The events are recorded and a specific test menu is provided.
  • High electromagnetic compatibility.
  • The installation and subsequent maintenance of batteries is eliminated. The operating costs of the centre are reduced.
  • In self-powered mode start-up of the relay from 0.2 times of the nominal current in one phase ensures capacity to trip at low energy levels. In dual powered mode the relay starts-up from 0.1 times of the nominal current.
  • The line opening mechanism is activated either by means of a striker PRT, operated by the energy supplied by the relay itself, or by a coil using the TCM trip adapter in case it is necessary.
  • There are bistable magnetic indicators which indicate the trip cause, maintaining their position even though the relay loses the supply.
  • Two different sizes of SIA-C relay available by model list to fulfil all the needs of our customers and make the installation easier.
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