Accessories for Medium Voltage Distribution Networks
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Saves Your Energy Accessories for Medium Voltage Distribution Networks Certified quality

Safe, energy efficient and environmentally friendly solutions Ensto is a family business and international cleantech company specializing in the development, manufacture and marketing of electrical systems and supplies for the distribution of electrical power as well as electrical applications. We are committed to lasting sustainable development and our goal is to be the world’s leading company in green energy efficiency and distribution. Our products are environmentally friendly, energy efficient and leave a minimum carbon footprint. Ensto has three key business units: Ensto Utility...

Functional Solutions Ensto´s solutions are reliable, installationfriendly and a good example of well-known Finnish engineering. Our products are desig­ ned for a long service life and a low lifecycle impact on environment. Ensto’s solutions are developed in close cooperation with our customers. We have thorough knowledge of distribution networks even in the most demanding circumstances in cold, hot and stormy surroundings all over the world. Focus on Energy Efficiency Ensto is committed to building sustainable energy infrastructure. Our low and medium voltage solutions are used to support...

Ensto Solutions for Various Medium Voltage Systems Ensto has developed integrated product packages and solutions for various medium voltage overhead lines from Covered Conductors (CC) and Universal Cables to Bare Conductors. Ensto accessories for medium voltage include e.g. insulators, tension and suspension clamps, arc protection devices, current limiting devices, connectors, bird protectors, crossarms and tools.

Covered Conductor System Plastic covered conductors without metal sheaths were developed to improve reliability of the distribution and transfer of electricity. Several years in use have proven the covered conductor system to be extremely functional and reliable. Interruptions and faults caused by snow, ice or storms have diminished remarkably. Using the Covered Conductor system offers also considerable space savings as the space required is approximately 40 % less than that of a standard bare line. This means e.g. narrow line corridors and space savings in substations. Parallel line...

Covered Conductor Systems Costs and general requirements Covered Conductor (CC) line construction costs are moderate, considering their advantages over traditional bare line structures. When constructing parallel lines, the costs of bare and CC lines are the same. Compared to traditional bare conductor construction, some additional requirements have been set for covered conductors. The most important requirements include: • Conductors must be handled with care • Only accessories designed and approved for the conductor may be used • Arc protection devices must be used on lines vulnerable to...

Arc protection can be accomplished using the following methods: • Arc protection device (APD) • Power arc device (PAD) • Surge arrester • Current limiting device. The protection chosen also depends on the network’s short-circuit values. The adjoining table displays the selected phase spacing of the covered conductors, the value of the short-circuit current with a protected object, and the recommended arc protection devices. Crossarm type Phase spacing over 60 cm Protection methods Power arc device, surge arrester, current limiting device Arc protection device with double wire, power arc...

Power Arc Devices Power Arc Devices With small short-circuit currents, an arc will move slowly and stress the insulator for a prolonged period. To avoid damage to the insulator, the arc must be ignited directly in the spark gap (1), so that the short circuit occurs through the crossarm (2) and trips the circuit breakers. The spark gap can also withstand the stresses of high short-circuit currents (Ik = 10 kA/1 sec). Power arc devices are not dependent on the direction of power feed and therefore can be installed on either side of the insulator. Power arc devices can also be installed on...

Horizontal Crossarms A spark gap is formed using the complete set SDI20.3 or SDI21.3, containing an arc protection connector and a mounting iron for the cross­ rm a pin, equipped with an arcing horn. Three SDI20.3 or SDI21.3 series are required per crossarm. The spark gap may be located on either side of the insulator; the effectiveness of the protection not being dependent on the direction of the power feed. The spark gap should be set to 100-150 mm. Crossarm for Line Angle The best method on crossarms is to use the suspension clamp with pulling wheel SO181.6, accessory kit SDI27.1 (see p....

Angle with Tension Insulators When constructing an angle with tension insulators installed in vertical line formation, arcing horns SDI27.1 must be used for tension insulator SDI90.X. The bolts must always be connected behind the pole with a vertical iron, e.g. PEK68, or a conductor (min. Cu 50 mm2). This prevents short-circuiting through the pole. Otherwise, the structures as for crossarms for line angle should be used. Terminal Crossarm with Spark Gap For the termination or tension of a convered conductor the best method is to use tension clamp SO255 or SO256 and tension insulator SDI90.X...

Main Line Bare Conductor / Branch Line CC The best and easiest way to implement arc protection at a branch pole is to install the SDI27.1 spark gap set with tension clamp SO255 or SO256, so that the conductor does not need to be stripped. It is also possible to use the SDI10.2 and SO85. When using a spark gap on the tension insulators of the branch conductor, the connecting conductors can be bare or covered. Main Line CC / Branch Line CC or Bare Conductor The main line shall be equipped with spark gaps. The connectors may be positioned freely, and the connecting conductors may be either...

Current Limiting Devices The economical way to protect a conductor is to use a current limiting device rather than only a surge arrester. The advantage is based on selecting a smaller surge arrester. Under normal operating conditions the smaller surge arrester is not stressed at line voltage, as its other end is in the air. This protection method also provides consumers with an uninterrupted electricity supply, because the arc protection does not cause high-speed auto-recloser operations. A surge arrester should be installed in the crossarm in the same way as an arcing horn. Installation...