Section 4. Switchgears and substations

Switchgears and substations with voltages above 1 kV. Installation of power transformers and reactors

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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4.2.203. The requirements given in 4.2.204 - 4.2.236 apply to stationary installation indoors and outdoors of power transformers (autotransformers), control transformers and oil-filled reactors with a higher voltage of 3 kV and higher and do not apply to special-purpose electrical installations.

The transformers, autotransformers and reactors referred to in this section are referred to in 4.2.204 to 4.2.236 by the term "transformers".

Installation of auxiliary equipment of transformers (electric motors of the cooling system, instrumentation, control devices) must comply with the requirements of the relevant chapters of these Rules.

Requirements 4.2.212, 4.2.217, 4.2.218 do not apply to the installation of transformers included in the PTS with a higher voltage up to 35 kV.

4.2.204. In regions with a cold climate, with increased seismicity, transformers of the appropriate design should be used.

4.2.205. The installation of transformers should provide convenient and safe conditions for its inspection without removing the voltage.

4.2.206. The foundations of transformers with a voltage of 35-500 kV should provide for their installation directly on the foundation without carriages (rollers) and rails.

Transformers at substations with stationary devices for repairing transformers (towers) and rolling rails, as well as at substations with transformers located in enclosed spaces, should be installed on carriages (skating rinks).

Seismic-resistant transformers are installed directly on the foundation with their fastening to the embedded foundation elements to prevent their displacement in the horizontal and vertical directions.

Places for installation of jacks must be provided on the foundations of transformers.

4.2.207. The slope of the oil transformer, necessary to ensure the flow of gas to the gas relay, must be created by installing pads.

4.2.208. When installing the expander on a separate structure, it must be located in such a way as not to prevent the transformer from rolling out from the foundation.

In this case, the gas relay must be located close to the transformer within easy and safe service from a fixed ladder. You can use the transformer bay portal to install the expander.

4.2.209. Transformers must be installed so that the opening of the oil ejection protection device is not directed towards closely installed equipment. To protect the equipment, it is allowed to install a protective shield between the transformer and the equipment.

4.2.210. Anchors should be provided along the rolling paths, as well as at the foundations of transformers weighing more than 20 tons, allowing winches, guide blocks, pulley blocks used for rolling transformers in both directions to be fixed to them. Places for the installation of jacks should be provided in places where the direction of movement changes.

4.2.211. Clear distances between openly installed transformers are determined by technological requirements and must be at least 1,25 m.

4.2.212. Dividing partitions between openly installed transformers with a voltage of 110 kV and above with a unit capacity of 63 MVA and more should be provided for:

• at distances of less than 15 m between transformers (reactors), as well as between them and transformers of any capacity, including adjusting and auxiliary ones;
• at distances of less than 25 m between transformers installed along the outer walls of power plant buildings at a distance of less than 40 m from the walls.

Dividing partitions must have a fire resistance limit of at least 1,5 hours, a width - not less than the width of the oil receiver and a height - not less than the height of the higher voltage bushings of a higher transformer. Baffles must be installed outside the oil receiver. The clear distance between the transformer and the partition must be at least 1,5 m.

The specified distances are taken to the most protruding parts of the transformers.

If auxiliary or control transformers are installed with a power transformer equipped with an automatic stationary fire extinguishing device and connected in the area of ​​protection against internal damage of the power transformer, then it is allowed to perform an automatic stationary fire extinguishing installation of the auxiliary or control transformer, combined with a power fire extinguishing installation, instead of a dividing partition. transformer; at the same time, the construction of a common oil receiver is allowed.

4.2.213. Regulating transformers should be installed in close proximity to regulated autotransformers, except for the case when a current-limiting reactor is provided between the autotransformer and the regulating transformer.

4.2.214. Automatic fire extinguishing installations are equipped with:

• transformers with a voltage of 500-750 kV, regardless of power, and a voltage of 220-330 kV with a capacity of 250 MVA or more;
• transformers with a voltage of 110 kV and above with a capacity of 63 MVA and more, installed in substation chambers and near hydroelectric power station buildings;
• transformers with a voltage of 110 kV and above of any power, installed in the underground building of a hydroelectric power station and a pumped storage power plant.

4.2.215. The fire extinguishing installation must be started automatically, manually and remotely from the control panel. The manual release device must be located close to the plant in a safe place in case of fire.

Switching on the fire extinguishing installation of a group of single-phase transformers should be carried out only on damaged phases.

4.2.216. Each oil transformer placed indoors should be installed in a separate chamber (exception 4.2.98) located on the first floor. It is allowed to install oil transformers on the second floor, as well as below the floor level of the first floor by 1 m in non-flood areas, provided that it is possible to transport transformers outside and remove oil in emergency cases in accordance with the requirements given in 4.2.103, as for transformers with a volume oils over 600 kg.

If it is necessary to install transformers indoors above the second floor or below the floor of the first floor by more than 1 m, they must be with a non-combustible environmentally friendly dielectric or dry, depending on environmental conditions and production technology. When placing transformers indoors, one should also be guided by 4.2.85.

It is allowed to install in one common chamber two oil transformers with an oil volume of up to 3 tons each, having a general purpose, control, protection and considered as one unit.

Dry transformers and having non-combustible filling are installed in accordance with 4.2.118.

4.2.217. For transformers installed indoors, clear distances from the most protruding parts of transformers located at a height of 1,9 m or less from the floor should be:

• to the back and side walls at least 0,3 m - for transformers with a capacity of up to 0,63 MB·A and 0,6 m - for transformers of higher power;
• from the entrance side to the door leaf or protruding parts of the wall, at least: 0,6 m - for transformers with a capacity of up to 0,63 MVA; 0,8 m - for transformers up to 1,6 MVA and 1 m - for transformers with a capacity of more than 1,6 MVA.

4.2.218. The floor of the chambers of oil transformers must have a 2% slope towards the oil receiver.

4.2.219. In the chambers of transformers, disconnectors, fuses and load switches, valve arresters, surge arresters, grounding arc-suppressing reactors, as well as equipment of the cooling system can be installed.

4.2.220. Each chamber of oil transformers must have a separate exit to the outside or to an adjacent room of category D or D.

4.2.221. The horizontal distance from the opening of the gate of the transformer chamber of the built-in or attached substation to the opening of the nearest window or door of the room must be at least 1 m.

Rolling out transformers with a capacity of 0,25 MVA or more from the chambers into internal passages less than 5 m wide between buildings is not allowed. This requirement does not apply to cameras facing the aisles and driveways inside the production premises.

4.2.222. The ventilation system of the transformer chambers must ensure the removal of the heat generated by them (4.2.104) and must not be connected to other ventilation systems.

The walls of ventilation ducts and shafts must be made of materials with a fire resistance rating of at least 45 minutes.

Ventilation shafts and openings must be located in such a way that in case of formation or ingress of moisture into them, it cannot flow onto the transformers, or measures must be taken to protect the transformer from moisture from the shaft.

Ventilation openings must be closed with meshes with a mesh size of not more than 1x1 cm and protected from rain and snow entering through them.

4.2.223. Exhaust shafts of oil transformer chambers attached to buildings with roofs made of combustible material must be separated from the walls of the building by at least 1,5 m, or roof structures made of combustible material must be protected by a parapet of non-combustible material with a height of at least 0,6 m. The output of the mines above the roof of the building in this case is optional.

Exhaust shaft openings should not be located against the window openings of buildings. When arranging outlet ventilation openings directly in the chamber wall, they should not be located under protruding roofing elements made of combustible material or under openings in the wall of the building to which the chamber adjoins.

If there is a window above the door or the outlet ventilation opening of the transformer chamber, then a visor made of non-combustible material with a projection of at least 0,7 m should be arranged under it. The length of the visor should be at least 0,8 m more than the width of the window in each direction.

4.2.224. Transformers with a forced cooling system must be equipped with devices for automatic start and stop of the cooling system.

Automatic start-up should be carried out depending on the temperature of the upper layers of oil and, regardless of this, on the load current of the transformer.

4.2.225. When using remote cooling devices, they must be placed so as not to prevent the transformer from rolling out from the foundation and allow their maintenance when the transformer is running. The air flow from the blast fans must not be directed towards the transformer tank.

4.2.226. The location of the valves of the cooling devices should provide convenient access to them, the possibility of disconnecting the transformer from the cooling system or a separate cooler from the system and rolling out the transformer without draining the oil from the coolers.

4.2.227. Cooling columns, adsorbers and other equipment installed in the C cooling system (OFWF) must be located in a room where the temperature does not drop below +5 ºС.

At the same time, it should be possible to replace the adsorbent on site.

4.2.228. External oil pipelines of DC (OFAF) and C (OFWF) cooling systems must be made of stainless steel or corrosion-resistant materials.

The location of oil pipelines near the transformer should not impede the maintenance of the transformer and coolers and should ensure minimal labor costs when rolling out the transformer. If necessary, platforms and ladders should be provided to provide convenient access to valves and blast fans.

4.2.229. For a remote cooling system consisting of individual coolers, all single or dual coolers placed in one row must be installed on a common foundation.

Group cooling units can be placed both directly on the foundation and on rails laid on the foundation, if it is planned to roll out these units on their rollers.

4.2.230. Control cabinets for electric motors of the DC (OFAF), NDC (ODAF) and C (OFWF) cooling system must be installed outside the oil receiver. It is allowed to hang the control cabinet of the cooling system D (ONAF) on the transformer tank, if the cabinet is designed to operate under conditions of vibration generated by the transformer.

4.2.231. Transformers with a forced cooling system must be equipped with an alarm to stop the circulation of oil, cooling water or stop the fans, as well as to automatically turn on or off the backup cooler or backup power source.

4.2.232. Electric heating with automatic control must be provided for cabinets of drives for voltage regulation devices under load and cabinets for automatic control of the transformer cooling system.

4.2.233. Scheduled preventive maintenance of transformers at substations should be provided at the place of their installation using truck cranes and (and) inventory devices. At the same time, a platform should be provided next to each transformer, designed to accommodate elements removed from the repaired transformer, rigging equipment and equipment necessary for repair work.

In cramped conditions of the substation, it is allowed to provide for one repair site with the construction of rolling paths to it.

At substations located in remote and hard-to-reach areas, combined portals should be provided.

At substations with a voltage of 500-750 kV located in areas with underdeveloped and unreliable transport links, as well as at outdoor switchgear of power plants when transformers are installed on them, if transformers cannot be delivered to the installation site of hydroelectric power plants and the repair site of the machine room of the power plant, for scheduled preventive maintenance works, it is allowed to provide for stationary devices - towers equipped with overhead cranes, with a workshop or oil facilities with a collector for mobile units.

The need to build a tower is determined by the design task.

4.2.234. When transformers are installed openly along the machine room of the power plant, it should be possible to roll the transformer to the repair site without disassembling the transformer, removing the bushings and dismantling the supporting structures of current ducts, portals, bus bridges, etc.

4.2.235. The lifting capacity of the crane in the transformer tower must be calculated for the mass of the removable part of the transformer tank.

4.2.236. Longitudinal ways of transformers rolling at substations should be provided for:

• if there is an access railway;
• in the presence of a tower for the repair of transformers;
• during emergency commissioning of the reserve phase of the autotransformer by the rolling method, if this is justified in comparison with other methods.

See other articles Section Rules for the installation of electrical installations (PUE).

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