Primary Substations and Switching Stations

Object Definition

Primary substation - a place, where a transmission network is connected to a distribution network, where high voltage is transformed to medium voltage. The medium voltage is divided into separate electricity distributions for specific areas.

Switching stations - a voltage transformation is not realized here, only medium voltage level distribution network is further divided.

Description of the Situation

Remote control of primary substations and switching stations has been and still is a priority in the most of distribution companies. Primary substation is the node point and the most important element of distribution grid, so eventual failure has a major impact on a large part of distribution network in specific location. That’s why it is very important to not only disconnect existing fault and protect affected part of the line from destruction, but also identify the affected line and the exact location of the fault as quickly as possible, that the service team can eliminate the fault in the shortest possible time.

Depending on the location of individual devices installed in the substations, all signals and communication lines can be transmitted to a single location (centralized system), or it is possible to place several smaller Remote Terminal Units (RTU) directly into the specific technology and then link them together – ideally by back-up communication (optimally redundant ring) to the data concentrator (RTU, which communicates with SCADA), and create a decentralized system by that.

ELVAC RTU Solution

ELVAC RTU systems in primary substations are used for:

  • collection of digital signals from multiple contacts from different switches, grounding knives and other technological alarms,
  • control of switching elements, tap changer control of transformers for voltage correction in power lines and switching to the backup line (bus) in case of power outage,
  • measurement of voltages, currents and derived quantities (power outputs, power factors etc.) on primary high voltage (HV) side  is usually done either by downloading these data from the protection relays that need this information for their own operation, on secondary medium voltage (MV) side either over protection relays or by measuring these quantities directly into RTU system through measuring transformers and calculating derived quantities,
  • data collection from many different substation devices.

This topic is covered in more detail in the application guide

ELVAC RTU benefits:

  • the possibility of the centralized or decentralized system with backup communication via an optical ring,
  • support for many communication protocols and interfaces, suitable for new installations and retrofits,
  • main and backup communication support to SCADA,
  • data concentrator function,
  • integration of protective functions for medium voltage - RTU can be used directly as protection relay at these levels, one RTU can replace up to 4 protection relays,
  • optional use of automation functions such as automatic backup (switching to backup lines in the case of a failure), or others,
  • integrated HMI interface - easy visualization of controlled technology.
  • optional battery backup - RTU directly charges and constantly monitors battery status.