Common use of Current transformers Clause in Contracts

Current transformers. Current transformers shall be single phase, secondary ratio transformers for outdoors assembly, in vertical position, with oil immersed or SF6 gas insulation and will be hermetically sealed. They shall be able to conduct the primary rated current for one minute, while the secondary circuit is open. The core shall be toroidal and made up of steel magnetic foils with very low specific losses, and the windings shall be made of insulated copper. In the case of the transformers that work in connection with the disconnectors, high frequency currents and voltages transferable to secondary and ground circuits shall be taken into consideration during the switching of adjacent live disconnectors. The manufacturer’s structural design shall be such that it prevents: g1) High current density in certain points of the equipment causing localized overheating. g2) Internal surges of very short duration causing dielectric breakdowns in liquid and solid insulators. Current transformers shall have the following additional characteristics: Description 220 kV Normal current 500 - 1000 A (L.T) Coupling (*) Secondary current 1 A Short-circuit thermal intensity 40 kA Characteristics of measurement cores a) Accuracy class b) Power 0,2 % 15 VA (minimum) Characteristics of protection cores a) Accuracy class b) Power 5P20 15 VA (minimum)

Current transformers. Current transformers shall be single phase, secondary ratio transformers for outdoors assembly, in vertical position, with oil immersed or SF6 gas insulation and will be hermetically sealed. They shall be able to conduct the primary rated current for one minute, while the secondary circuit is open. The core shall be toroidal and made up of steel magnetic foils with very low specific losses, and the windings shall be made of insulated copper. In the case of the transformers that work in connection with the disconnectors, high frequency currents and voltages transferable to secondary and ground circuits shall be taken into consideration during the switching of adjacent live disconnectors. The manufacturer’s structural design shall be such that it prevents: g1) High current density in certain points of the equipment causing localized overheating. g2) Internal surges of very short duration causing dielectric breakdowns in liquid and solid insulators. Current transformers shall have the following additional characteristics: Description 220 kV Normal current 500 - 1000 A (L.T) Coupling (*) Secondary current 1 A Short-circuit thermal intensity 40 kA Characteristics of measurement cores a) Accuracy class b) Power 0,2 % 15 VA (minimum) Characteristics of protection cores a) Accuracy class b) Power 5P20 15 VA (minimum)) (*) Value to be defined in the Pre-operation Study.

Current transformers. Current transformers shall be single phase, secondary ratio transformers for outdoors assembly, in vertical position, with oil immersed or SF6 gas insulation and will be hermetically sealed. They shall be able to conduct the primary rated current for one minute, while the secondary circuit is open. The core shall be toroidal and made up of steel magnetic foils with very low specific losses, and the windings shall be made of insulated copper. In the case of the transformers that work in connection with the disconnectors, high frequency currents and voltages transferable to secondary and ground circuits shall be taken into consideration during the switching operation of adjacent live disconnectors. The manufacturer’s structural design shall be such that it prevents: g1) . High current density in certain points of the equipment causing localized overheating. g2) . Internal surges of very short duration causing dielectric breakdowns in liquid and solid insulators. Current transformers shall have the following additional characteristics: Description 220 kV Normal 60 kV Continuous service current 500 000 - 1000 000 X (X.X) 000 - 000 A (Transformer) (*) 300 - 600 A (L.T) Coupling 400 - 800 A (Transformer) (*) Secondary current 1 A 1 A Short-circuit thermal intensity 40 kA 31.5 kA Characteristics of measurement cores a) Accuracy class b) Power 0,2 % 15 VA (minimum) 0,2 % 15 VA (minimum) Characteristics of protection cores a) Accuracy class b) Power 5P20 15 VA (minimum)) 5P20 15 VA (minimum) (*) Current relationship to be supported in the POS.

Current transformers. Current transformers shall be single phase, secondary ratio transformers for outdoors assembly, in vertical position, with oil immersed or SF6 gas insulation and will be hermetically sealed. They shall be able to conduct the primary rated current for one minute, while the secondary circuit is open. The core shall be toroidal and made up of steel magnetic foils with very low specific losses, and the windings shall be made of insulated copper. In the case of the transformers that work in connection with the disconnectors, high frequency currents and voltages transferable to secondary and ground circuits shall be taken into consideration during the switching operation of adjacent live disconnectors. The manufacturer’s structural design shall be such that it prevents: g1) . High current density in certain points of the equipment causing localized overheating. g2) . Internal surges of very short duration causing dielectric breakdowns in liquid and solid insulators. Current transformers shall have the following additional characteristics: Description 220 kV Normal 60 kV Continuous service current 500 300 - 1000 600 A (L.T) Coupling 300 - 600 A (Transformer) (*) 300 - 600 A (L.T) 400 - 800 A (Transformer) (*) Secondary current 1 A 1 A Short-circuit thermal intensity 40 kA 31.5 kA Characteristics of measurement cores a) Accuracy class b) Power 0,2 % 15 VA (minimum) 0,2 % 15 VA (minimum) Characteristics of protection cores a) Accuracy class b) Power 5P20 15 VA (minimum)) 5P20 15 VA (minimum) (*) Current relationship to be supported in the POS.