Measuring current transformers. Production.
►technical requirements of the concern «BelEnergo» for measuring current transformers, in addition to the requirements of GOST 7746 - 2001
1. Measuring current transformers of low voltage networks for commercial metering of electricity must comply with an accuracy class of at least 0.5 S and have a rated secondary load of not more than 5 VA.
2. All measuring current transformers must be entered into the State Register of Measuring Instruments of the Republic of Belarus and undergo technical certification at the Belenergo Concern.
3. All measuring current transformers must be metrologically verified, sealed and have a corresponding mark in the passport.
4. Requirements for the design of current transformers
4.1 Housing parts of measuring current transformers must be of a flame resistance category of at least PV-0.
4.2 Instrument current transformers must have primary busbars for mounting to copper and aluminum busbars and wires (busbar lengths must correspond to the order card).
4.3 Instrument current transformers must have fasteners for connecting the busbars and fixing the transformer in the electrical installation, including on a DIN rail (according to the order card).
4.4 Instrument current transformers should allow changing the orientation of the busbar for transformers with primary rated currents (200-600) A.
4.5 The connecting dimensions of the transformers must correspond to the previously used dimensions (according to the order card).
4.6 The data plate (material and inscription) must guarantee the safety of information throughout the entire service life (25 years).
5. Protection of current transformers from theft of electricity
5.1 Exclude the possibility of replacing the plate and disassembling current transformers without damaging their cases, protective parts, seals.
5.2 After the installation of the current transformers and their sealing, access to the contacts of the secondary winding must be excluded.
5.3 It should be possible to seal each current transformer with two independent seals (the seal of the metrological service and the power supply organization).
5.4 The current transformer must have a sealable voltage circuit contact permanently connected to the primary bus.
5.5 The current transformer must be permanently marked with the transformation ratio.
Based on the above, the «BelEnergo» concern obliged:
1. RUE - oblenergo and JSC "Belenergosnabkomplekt":
1.1 In tenders for the purchase of 0.5S class instrument transformers for 0.4 kV distribution power grids, select only modern instrument current transformers that meet these technical requirements.
1.2 To gain experience in operating current transformers with nanocrystalline alloy cores, ensure the purchase of pilot batches of these transformers in the amount of at least 10% of the total purchased quantity.
2. RUE - oblenergo ensure that these technical requirements are taken into account when agreeing on design solutions for organizing calculated electricity metering at consumers.
3. To bring this instruction to the attention and execution of the personnel of RUE - oblenergo divisions.
4. Control over the implementation of this Order shall be entrusted to the Energy Sales Department of the «BelEnergo» Concern, locally - to the chief engineers of RUE - oblenergo.
Thus, at present, the united power system of the Republic of Belarus envisages, within the framework of modernization, the replacement of current transformers of class 0.5 with current transformers of class 0.5S, and in accordance with scientific and technical progress, the replacement of low-voltage current transformers on cores made of electrical steel with transformers current with cores made of nanocrystalline alloys. Moreover, since local manufacturers of three-phase electricity meters of transformer switching of accuracy class 0.2S have now appeared in the Republic of Belarus Gran-Electro SS-301 (K) (manufactured by NP LLC «Gran-Sistema-S», RB, Minsk) and measuring current transformers TOP-N-0.66 and TShP-N-0.66 on cores made of nanocrystalline alloy of accuracy class 0.2s (manufactured by LLC «Yudzhen», RB, Novopolotsk), the replacement of current transformers is just around the corner accuracy classes 0.5 and 0.5S for current transformers of class 0.2S and the emergence of more energy efficient and accurate AMR systems based on them.
Measuring current transformers.