IEC 60076-22-3-2019 pdf download.Power transformers — Part 22-3: Power transformer and reactor fittings — Insulating liquid to air heat exchangers
Transformateu de puissance Partie 22-3: Accessoires pour transformateurs de Puissance et bobines dinductance — Aéroréfrigerants.
The normal service conditions set out in IEC 60076-1 represent the normal scope of operation of the device and equipment specified ri this document.
Device and equipment specification for operation under unusual service conditions as per IEC 60076-1 shall be subject to agreement between the purchaser and supplier, as they require special consideration in the design of the device and equipment.
In addition to the unusual service conditions of IEC 60076-1, any unusual condition, which can influence the correct functioning of the cooler, shall be mentioned, such as heavy snow, permanent wind, pollen, sealing dust.
4.2 Degree of protection of electrical components (IP)
The degree of protection of the connecting box or terminal box for an outdoor installation shall
be at least lP 54 according to IEC 60529, unless otherwise specified by the purchaser.
4.3 Corrosion protection
4.3.1 External (atmosphere)
The materials used for the construction of the equipment or the surface treatment shall be resistant to accidental contact with the insulating liquid and suitable to withstand the environmental conditions given in 4.1. The corrosion protection shall be agreed between purchaser and manufacturer according to ISO 12944 (all parts). The responsibility to specify the correct level of corrosion protection lies with the purchaser and is dependent on the environment where the transformer will be located and on the durability required. Unless otherwise specified, the minimum withstand level shall be C4 medium durability according to
ISO 12944-6.
4.3.2 Insulating liquid side
In consideration of the storage conditions and expected time between shipment and commissioning, the corrosion protection on the insulating liquid side of the cooling system shall be agreed between purchaser and manufacturer. As a minimum requirement, precautions shall be taken to prevent the ingress of moisture and the development of internal corrosion. The internal flushing with insulation liquid fully miscible and compatible with the liquid to be used in service conditions and the use of blanking plates with gaskets are considered as a minimum. Internal painting, nitrogen filling, dehydrating material, etc., can be used as other or additional solutions.
4.4 Insulating liquid characteristics
If not otherwise specified, the insulating liquid is mineral oil according to IEC 60296 and the operating temperature shall be in accordance with IEC 60076-7.
When the insulating liquid is not mineral oil then the purchaser shall indicate the viscosity variation, the operating temperature and all the other operating characteristics.
5 Design and characteristics
5.1 Main components and characteristics
5.1.1 Headers
Liquid collecting and guiding compartment with flanged connections to the circuit of the transformer.
5.1.2 Tube sheets
Flat plates at both ends of the cooler where the cooling tubes are connected.
5.1.3 Tube bundle
Consisting of a bundle of single tubes and fins connected to both tube sheets Tubes might have different shapes and can be made of different materials.
5.1.4 Turbulators
Inserts inside the tubes aimed at enhancing the cooling efficiency.
5.1.5 Passes
Number of times the insulating liquid flows through the exchanger. For instance, the number of passes 1” means that the liquid is flowing one way from one header to the other (liquid inlet and outlet in the opposite headers).
5.1.6 Standard design and cooling arrangement
The liquid to air heat exchanger arrangement can be with:
• vertical cooling pipes and horizontal air direction;
• horizontal cooling pipes and horizontal air direction;
• horizontal cooling pipes and vertical air direction;
• forced-draught type or induced draught type fan arrangement can be used.
5.2 General characteristics.IEC 60076-22-3-2019 pdf download.Power transformer and reactor fittings — Insulating liquid to air heat exchangers