Kontaktledning/Autotransformatorer

< Kontaktledning


Innhold

1 PURPOSE

This standard (in Trafikverket caled BVS) or technical specification (in Jernbaneverket), which is an English version of BVS 543.14513, has been drawn up in order to standardize the manufacturing of 3 and 5 MVA autotransformers.

The document is a joint publication by Banverket (the Swedish Rail Administration) and Jernbaneverket (the Norwegian National Rail Administration).

Proposals for alteration regarding this BVS shall be put to the Power Systems Section at Banverket’s Operations Division.


2 SCOPE

In this BVS, Banverket and Jernbaneverket make their demands on design of autotransformers with a rated output of 3 and 5 MVA regarding electrical and mechanical performance and surface treatment. Requirements for testing and documentation are also stated.

The document does not comprise design of and requirements for the concrete foundation including the superstructure, in which the autotransformer will be installed.

The document shall be applied in connection with Banverket’s public procurements.

The document is intended for tenderers.

3 DEFINITIONS AND ABBREVIATIONS

3.1 Definitions

Operating side

The side of a transformer that is the easiest accessible when the transformer has been installed in its superstructure

Additional definitions of terms used in this document are found in EN 50163

3.2 Abbreviations

AT

Autotransformer

BT

Booster transformer

AT system

Power supply system with autotransformers

BT system

Power supply system with booster transformers

AT-BT system

Power supply system with a combination of autotransformers and booster transformers

BVS

Banverket standard

MTTF

Mean Time To Failure

PD

Partial Discharge


4 RESPONSIBILITY

Not relevant


5 TECHNICAL INFORMATION

5.1 Function and use

Autotransformers are used at present for transferring power in Swedish and Norwegian AT systems and will also be used in prospective AT-BT systems.

The supply voltage to an autotransformer shall be connectible in two ways: between outlet A and B at system voltage 30 kV, and between terminals A and 0 at system voltage 15 kV. Figur 1 shows a simplified diagram of an autotransformer and the most important parameters.

Figur 1

Figur 1: Simplified diagram of an autotransformer and the most important parameters










A = Terminal A (connected to the catenary wire or the positive wire in Norwegian systems)

0 = Terminal 0 (connected to S-rail [continuous rail]/grounding line)

B = Terminal B (connected to the feeder wire or the negative wire in Norwegian systems)

N1 = Number of turns in primary winding

N2 = Number of turns in secondary winding (here N1 = 2 × N2)

U1 = Voltage across the primary winding

U2 = Voltage across the secondary winding

I1 = Current in the primary winding

I2 = Current in the transformer’s centre terminal

ZT = Transformer’s inner reactance

The load is connected between terminals A and 0. With the turn ratio at N1/N2 = 2/1, the current between the two transformer terminals A and B (I1) is always the same, while the current through terminal 0 is double the winding current (I2 = 2 × I1).

Figur 2 and Figur 3 show the simplified principles of the Swedish and Norwegian AT systems.

Figur 2

Figur 2: Simplified sketch of a Swedish AT system










The spacing between the transformers is approximately 10 km. The transformers are not equipped with dedicated circuit breakers. An outgoing line circuit breaker connects and disconnects a number of in-parallel transformers along a line section.

Figur 3

Figur 3: Simplified sketch of a Norwegian AT system










One difference between the Swedish and the Norwegian AT systems is that the catenary system is sectionalized in Norway. Each contact wire section is connected to a through-going positive wire as shown in Figur 3.

5.2 Environmental factors

Tabell 1 shows the most important environmental factors that have to be considered in the dimensioning of the transformer and a number of references to relevant standards.

Tabell 1: Parameters and values for environmental factors
Parameter Value
Nominal voltage (Un) 15 kV (+15 to -20 %)
Operational voltage (Ud) 16.5 kV
Voltage variations In accordance with EN 50163 with Ucrest < 35 kV
Total harmonic distortion
UTHD up to 40 %
Typical distribution of the dominant voltage harmonics
(UTHD = 30 %):
n %
(harmonics no.) (relative to fundamental tone of voltage)
3 24
5 16
7 4
Total harmonic distortion in the load current
ITHD up to 60 % (at the rated current of the transformer)
N %
(harmonics no.) (relative to rated current of locomotive)
3 5
5 3
7 3
9 3
Frequency 16,7 Hz (± 1/3 Hz)
Ambient and operating temperatures

Sweden:
South of Dalälven river: -40 to +40 ºC
North of Dalälven river: -50 to +40 ºC

Norway:
-40 to +40 ºC

Load cycle (repeated every hour, load as % of rated output)

100 % for 39 minutes followed by
150 % for 15 minutes followed by
200 % for 5 minutes followed by
300 % for 1 minute

Sub-transient short-circuit currents (Ik’’) associated with faults between the catenary and the rails or between the feeder wire and the rails

Short-circuit current through the centre terminal: 12 kA at 16.5 kV
Short-circuit current in each winding: 6 kA
Disconnection time associated with short-circuit: < 0.6 seconds

Maximum surge current (Ip) associated with a fault between the catenary and the rails or between the feeder wire and the rails 2.55 × Ik’’ = 30 kA
Number of on operations Up to four times per 24 hours
Fault frequency in the catenary system Up to 1 fault per km and year

5.3 Dimentioning data

Tabell 2 shows dimensioning data for autotransformers with rated outputs of 3 and 5 MVA.

Tabell 2: Dimensioning data for autotransformers with rated outputs of 3 and 5 MVA
Transformer type Single-phase autotransformer
Rated output (through-going output/dimensional out-put [MVA]) 3.0/1.5 5.0/2.5
Rated voltage (Un1/Un2) [kV] 33/16.5 33/16.5
Rated current (In1/In2) [A] 90.9/181.8 151.5/303
Rated frequency [Hz] 16.7
Dimensioning short-circuit current At least 50 short-circuit operations with 12 kA through the centre terminal of the transformer (6 kA per winding).

See special test in section Short-circuit testing

Short-circuit impedance (ZT) [[math] \Omega [/math]] or [%]
Derivation and feed in accordance with section Routine tests
≤ 0.218 +0/-10 % for 5 MVA
or 0.4 % in general for other ratings.
Turn ratio (N1/N2) 2/1
Insulation level LI 170, AC 70
Housing class IP 55
Coolant type ONAN
Noise level Sweden:

Target value for noise from transformer structures is 50 dB(A) and is based on the relevant norms of the National Housing Board.
The maximum sound output from individual transformers is 65 dB(A).

Functional safety (MTTF) To be stipulated in the tender
Aging factor (V) < 1 with the stated load cycle IEC 60076-7
Idling and full-load losses To be stated as a function of the through-going output.

Assessment of idling and full-load losses is to be carried out by the customer.

6 TECHNICAL PERFORMANCE

6.1 General considerations

The transformer is the main appliance in the AT and AT-BT systems, and there are high expectations regarding its reliability and proper dimensioning. One of the important factors that shall be considered in association with the dimensioning of the transformer is the connection and fault frequency in the catenary system.

The occurrence of short-circuit currents, together with the catenary system’s susceptibility to short-circuit, also places a high demand on the transformer’s mechanical dimensioning. The transformer’s active components (core and windings) shall have the same dimensioning for both 3 and 5 MVA.

The transformer shall be equipped and supplied in accordance with the requirements stated in this chapter. Depending on the construction of the transformer, some of the requirements might be deleted. If the supplier so desires, equivalent and more cost-effective procedures could be suggested for costly technical requirements.


6.2 Expansion vessel

If the transformer is fabricated with an expansion vessel, then the following applies:

a. The oil-containing component shall be hermetically sealed. The separation shall be made using a plastic bag.
b. Valves for air-filling shall be located in suitable sites on the transformer’s service side.
c. The expansion vessel and piping shall be painted on the inside.


6.3 Bottom valve

a. The bottom valve shall be located on the transformer’s service side.


6.4 Dehydrating breather equipment

a. Dehydrating breather equipment shall be fabricated of stainless steel material and located on the transformer’s service side.
b. Piping with connectors between the dehydrating breather and the expansion vessel shall be fabricated of stainless steel material.


6.5 Valves for oil sampling

a. Valves for taking oil samples shall be located at the top of the transformer tank, halfway up the tank, and at the bottom of the tank.
b. All valves shall be located in such a way that they are easily accessible; for example, on the transformer’s service side.
c. Necessary accessories (sleeves, connecting components, etc.) for taking oil samples shall be included in the delivery.


6.6 Monitoring equipment

6.6.1 Equipment types

a. Previously used equipment products and models shall be used as far as possible.


6.6.2 Gas and oil actuated relay (Buchholtz relay)

a. Gas and oil actuated relay shall be equipped with valves for shutting off flow on both sides and with a bypass piping with a valve.
b. Gas and oil actuated relays shall be connectable to the tank with a flexible metal hose.
c. The contact assembly shall be equipped with a closing contact for slow gas development (fault signal) and a closing contact for surges, low oil levels and rapid gas development (trip signal).
d. The contacts shall be suitable for 110 V DC and 230 V AC.
e. The contacts must not contain mercury.


6.6.3 Oil temperature gauges and oil temperature monitors

a. Oil temperature gauges and oil temperature monitors shall be of AKM (Kihlström) or equivalent manufacture.
b. Oil temperature gauges shall be equipped with separate closing contacts for fault and tripping signals.
c. Oil temperature monitors shall be equipped with indicating displays and resettable maximal displays.


6.6.4 Oil level indicators and oil level monitors for the expansion vessel

a. Oil level indicators and oil level monitors for the expansion vessel shall be of AKM (Kihlström) or equivalent manufacture.
b. Oil level indicators and oil level monitors for the expansion vessels shall be equipped with separate closing contacts for fault and tripping signals.


6.6.5 Cabling on the transformer

a. Shielded cables shall be used for connections between the equipment and the junction box.
b. All cabling to the transformer shall incorporate multiple conductors.
c. Signal cables shall have an area of 1.5 mm².
d. Current transformer cables shall have an area of 2.5 mm². Connections to the current transformer shall be made using cable lugs
e. Cables must not lie directly on the tank lid.
f. Cables shall be suitable for 110 °C.
g. Cabling shall be fastened using stainless steel cable straps.
h. Cables shall be protected against walking. This also applies to capillary tubing.
i. Cables shall be numbered in both ends. Strands shall be numbered with cable, strand and ter-minal numbers.
j. All metal components that are not welded towards the transformer tank or its cover shall be equipped with visible grounding connections.

6.7 Screw and bolt joints

a. Stud fasteners may be used if they are not spot-welded to the material. This requires a threaded hole in the construction.
b. Screws, studs, washers, pipe clamps and nuts in large sizes (> M8) located on the exterior of the transformer shall be made of heat-galvanized material.
c. Screws, studs, washers, pipe clamps and nuts in smaller sizes (< M8) located on the exterior of the transformer shall be made of stainless steel (A2).
d. Bolt-connected joints shall be fitted with flat washers closest to painted surfaces.


6.8 Sealing system

a. All sealing shall be of groove model; for example O-ring. For each such sealing, there shall be a fitted groove that limits the mechanical stress against the O-ring.
b. Sealings shall be oil-, ageing- and UV-light-resistant.
c. Synthetic cork gaskets and thread tape must not be used in the sealing system.


6.9 Instrument transformers

a. As an option 6.9a there shall be an current transformer for the "0" connection installed. It shall be possible to exchange current transformers only by dismantling the bushing for the "0" connection. The secondary side shall be ended in the transformer junction box. The transformer shall be build so it easily can be completed later with this option.
b. The current transformer shall have the following rating specifications:
Transformer ratio: 600/1 A
Frequency: 16.7 Hz
Power: 0.1-15 VA
Class: 0.5 FS ≤ 5 for measurement
c. As an option 6.9c there shall be two voltage transformers for 0-A and 0-B connections installed. It shall be possible to exchange voltage transformers from the tanktop. The secondary sides shall be ended in the transformers junction box via fuses. The transformer shall be build so it easily can be completed later with this option.
d. The voltage transformer shall have the following rating specifications:
Transformer ratio: 17000/110 V
Frequency: 16.7 Hz
Power: 1-20 VA
Class: 1.0 measuring

6.10 Equipment and junction box

a. The box shall be constructed in housing class IP55.
b. The box shall be located at ground level.
c. The box shall be very spacious and built from stainless steel sheeting.
d. To protect the box from rain and snow, a roof of stainless steel sheeting shall be erected to cover the entire box.
e. All cabling shall enter the box from below via metal fittings that have been tightly sealed. There shall be reserve holes in the junction box for cables.
f. Terminals in the box shall be of type Phönix URTK/S-BEN or equivalent.
g. The box shall be fitted on the inside with a heating element and a thermostat. Air vents shall be located at the top and bottom.
h. The box shall be equipped with a PE bus bar.


6.11 Transformer tank

6.11.1 General considerations

a. The transformer tank shall be pressure- and vacuum-proof.
b. The transformer tank shall be painted on the inside.


6.11.2 Ladder

a. There shall be a ladder leading to the top of the transformer tank.
b. The rungs shall be slip-proof.
c. The ladder shall be installed as far away from the tank as to allow a normal-sized foot to fit on the rungs.


6.11.3 Grounding connections

a. Grounding connectors shall be located on both sides of the transformer tank’s bottom section.


6.11.4 Lifting eyes

a. Lifting eyes shall be integrated into the tank construction.


6.11.5 Oil system

a. Insulating oil shall be of type "NYTRO 10XN" or equivalent.
b. The oil which the autotransformer is filled with at the test field must also be the same oil the transformer are filled with at site.
c. Insulating oil must not be corrosive according to CCD-CIGRÈ method.
d. Insulating oil shall be guaranteed free from PCBs (less than 2 ppm) and silicon.
e. The warranty period for oil leakage shall be established at the time the contract is signed. The warranty period shall be at least 10 years.
f. The oil-containing component shall be hermetically sealed.


6.11.6 Transformer tank cover

a. The transformer tank cover shall be welded towards the tank.


6.11.7 Centring point

a. The centring point of the transformer tank shall be clearly labelled.


6.11.8 Dimensions

a. The highest point shall be lower than 3740 mm from the bottom edge of the transformer tank (Figur 4).
b. The height of the tank, from its bottom edge to the tank lid, shall be 2840 mm (Figur 4).

Figur 4

Figur 4: Height of transformer tank and highest point (measured in mm)









6.12 Plates

All plates in sections Equipment plates and Rating plates shall be in Swedish when delivered to Trafikverket or in Norwegian when delivered to Jernbaneverket.


6.12.1 Equipment plates

a. All valves, bushings and devices shall be labelled with equipment plates showing their respective designations in accordance with the manufacturer’s drawings and diagrams. The plates shall be of stainless steel with engraved text. The plates shall be fastened with screws onto dedicated sign holders.


6.12.2 Rating plates

a. A rating plate shall be located on the transformer’s service side. The plate shall contain information in accordance with section 2.8 in EN 50329. The plate shall also indicate the oil type/manufacture, the temperature dependence of the oil level, and whether the expansion vessel is fitted with a plastic or a rubber bag.
b. Close to the rating plate there must be a plate showing oil level in expansion vessel versus oil temperature in expansion vessel.

6.13 Bushings and surge arresters

6.13.1 Bushings

a. Bushings shall be of “plug-in” type and installed in accordance with EN 50180.
b. Bushings shall be located on the transformer cover as shown in Figur 5.
c. There must be a bushing also for the grounding of the core on the tank cover. The grounding connection must be removable.

Figur 5

Figur 5: Location of bushings on the transformer cover (measured in mm)













6.13.2 Surge arresters

a. It shall be possible to install surge arresters in direct connection to the bushings A and B (Figur 1).
b. Any surge arrester and bushing that are installed, shall together with the appropriate cable terminations, be safe to touch.
c. Any surge arrester that are installed shall be dimensioned and selected with a view to the possible occurrence of over-voltages, as mentioned in section Environmental factors, and the insulation level of the transformer.

6.14 Surface treatment

6.14.1 Painting

a. For exterior painting, the rust-protective system cited in ISO 12944 is to be used. For exterior painting, corrosiveness class C3 and durability rating High apply in all parts of Sweden except the west coast. For the west coast of Sweden and all of Norway, corrosiveness class C4 and durability rating High apply.


6.15 Documentation

6.15.1 General considerations

a. All documents shall be provided in Microsoft Word or PDF format (one set) and be written in either Swedish or Norwegian.


6.15.2 Scope

Each transformer is to be accompanied by three sets of paper copies in binders and five sets of electronic copies in PDF format on a CD-ROM with the following content:

a. Layout drawings for the finished transformer.
b. Circuit diagrams, connection tables and equipment lists for the equipment installed inside and outside.
c. Oil level diagrams for the expansion vessel (level vs. outside temperature).
d. All quality-related documents for each transformer.
e. Test reports for routine tests (see section Routine tests), type tests (see section Type tests) and special tests (see section Special tests) of the transformer.
f. Equipment descriptions in their original form and, where appropriate, the same descriptions translated into Swedish or Norwegian.
g. Original instruction manuals for transformer maintenance and, where appropriate, the same manuals translated into Swedish or Norwegian.
h. Original instruction manuals for installation and commissioning and, where appropriate, the same manuals translated into Swedish or Norwegian.

7 CONSTRUCTION AUDIT

7.1 Scope

Before a transformer can be type-certified, construction audits are to be carried out in two stages:

  1. Prior to purchasing of the transformer that shall be type-certified
  2. After purchasing, in advance of delivery and type certification

All changes in construction or manufacturing procedures for a type-certified construction shall be immediately reported to the customer.


7.2 Construction audit prior to purchasing

In the course of the construction audit prior to purchasing, the tenderer shall state clearly, and give reasons for, any deviation from the requirements specified in the invitation to tender. The tenderer shall also present the basis data for the construction and dimensioning of the transformer to the customer. The basis data includes the information listed in sections Electrical rating to Weight.


7.2.1 Electrical rating

Below are examples of electrical rating data that shall be reviewed:

  • Rated voltages
  • Rated currents
  • Impedances
  • Rated outputs (through-going output and type output per winding)
  • Rated frequency
  • Transformer ratio
  • Insulation levels
  • Housing class


7.2.2 Losses

The transformer’s estimated losses shall be stated in the form of load loss as a function of through-going output and idling losses.


7.2.3 Physical dimensions

The physical dimensions of the transformer shall be specified.


7.2.4 Weight

The weight of the transformer shall be specified both with and without oil.

7.3 Construction audit after purchasing

Following purchasing and prior to the start of transformer manufacturing, a detailed construction audit shall be carried out. The supplier shall present the basis information to the customer in Swedish or Norwegian, or alternatively in English. The basis information shall include the information listed in sections Core to Procedures.


7.3.1 Core

a. Dimensions
b. Complete core construction
c. Flow description


7.3.2 Design of the windings

a. Diagram
b. Bracing
c. Cooling ducts
d. Dimensions of wiring and finished windings
e. Material specification for wiring and insulation
f. Manufacturing and inspection methods


7.3.3 Complete active part

a. Layout
b. Material specification for bracing and insulation components.
c. Connections between press girders
d. Connections between the upper and lower yokes
e. Design of axial and radial supports for the windings
f. Clamping pressure of windings
g. Bracing
h. Insulation components
i. Installation and clamping methods


7.3.4 Connections to bushings and between windings

a. Dimensions
b. Laying
c. Contacts


7.3.5 Equipment in and on the transformer

a. Gas and oil relay (Buchholtz)
b. Temperature gauges
c. Bushings
d. Oil coolers
e. Air coolers
f. Valves
g. Surge arresters


7.3.6 Vessels, tanks, pipes and painting

a. Review of drawings with a view to sealing and painting
b. Review of the painting system


7.3.7 Short-circuit conditions

a. Description of how the forces acting on individual windings in the event of short-circuit are calculated
b. Description of how the construction safeguards the transformer’s tolerance of all types of displace¬ment and deformation of windings, bracings and cores


7.3.8 Calculations

a. Description of how internal voltages in the transformer are calculated
b. Verifying of calculations through testing with low-voltage, short surges
c. Description of calculations to determine short-circuit impedance


7.3.9 Tolerances

a. Manufacturing tolerances for steel components
b. Tolerances for installation of steel components
c. Tolerances for installation of windings

7.3.10 Procedures

The supplier shall prepare procedures for the following:

a. Manufacturing follow-up by the design office in connection with delivery of the first unit
b. Quality control of the steel components
c. Painting of the steel components
d. Inspection of completed steel components
e. Quality control of the transformer
f. Installation of windings
g. Testing and documentation of the transformer
h. Quality assurance of the installation at the delivery site
i. Installation and commissioning at the installation site

8 TESTING

8.1 General considerations

The supplier shall carry out testing in accordance with this chapter. The supplier shall present a testing schedule to the customer at least three weeks before the start of testing. The customer shall at all times be given the opportunity to participate in the testing activities.


8.2 Scope and type certification

The scope of the testing to be carried out prior to delivery of a transformer depends on whether the transformer construction involved has been type-certified or not. If the purchase involves a transformer of new construction, or one from a new supplier, then an example of the transformer shall be subjected to testing that, if all the requirements are satisfied, will lead to type certification. This testing includes routine tests (section Routine tests), type tests (section Type tests) and special tests (section Special tests). Transformers that pass the routine tests, type tests and special tests, and that satisfy all the requirements outlined in chapters TECHNICAL INFORMATION, TECHNICAL PERFORMANCE and CONSTRUCTION AUDIT, are assumed to meet the criteria for certification. A type-certified transformer construction must not be altered in any way without prior approval of the change by the customer. If the purchase involves a previously certified construction, the pre-delivery testing is limited to routine tests and oil tests in accordance with section Testing of type-certified transformers.

8.3 Testing prior to type certification

8.3.1 General considerations

Following each test carried out prior to type certification, the customer shall receive an original version of the test report from the testing organization. If present at the test site, the customer shall receive a preliminary report before leaving.


8.3.2 Routine tests

Routine testing includes all the routine tests listed in EN 60076-1, section 10, and PD measurements in accordance with EN 60076-3, section 12.2.2.


8.3.3 Type tests

The type tests include insulation testing with lightning inpulse for all terminals in accordance with EN 60076-3, section 7, measurement of sound levels in accordance with EN 60076-10, and heat testing in accordance with EN 60076-2. The heat testing shall be carried out with the stated load cycle and shall include the dimensioning total harmonic distortion. The decision whether to perform heat testing with or without the outer housing is made on a case-by-case basis.

8.3.4 Special tests

The special tests include measurement and calculation of the zero phase-sequence impedance and short-circuit testing (testing of resistance to short-circuit).


8.3.4.1 Measurement and calculation of zero phase-sequence impedance

The transformer’s rated output (through-going output) Sn may be written as follows:

Sn = Un1 × In1 = Un2 × In2

In the case of a short-circuit across the primary winding (A and B terminals), a 16.7 Hz current (In1) is induced between A and 0. The short-circuit voltage (uk) that is required to achieve primary rated current (In1) shall be noted together with the measured current (I2). The transformer’s zero phase-sequence impedance is calculated using the following formula:

[math]Z_0 = {\dfrac{2 \times u_k}{I_2}}[/math]

<xr id="fig:Measurement of short-circuit voltage <nowiki>(uk)</nowiki> and zero phase-sequence impedance" /> <xr id="fig:Measurement of short-circuit voltage <nowiki>(uk)</nowiki> and zero phase-sequence impedance" />

(uk)</nowiki> and zero phase-sequence impedance">
Figur 6: Measurement of short-circuit voltage (''u<sub>k</sub>'') and zero phase-sequence impedance

Derivation: See<ref>Varju, G.: Method for calculating autotransformer and booster transformer railway supply systems by the two-phase symmetrical components. Budapest University of Technology, Hungary, 1997.</ref>

uk = I2 × ZT = u0 (zero sequence source !)

N1/N2 = 2

Also applicable is:

[math]I_2 = 2 \times I_0 \quad Z_0 = \dfrac{u_0}{I_0}[/math]

[math]Z_0 = \dfrac{Z_T \times I_2}{\left (\tfrac{I_2}{2} \right )} = 2 \times Z_T = \dfrac{2 \times u_k}{I_2}[/math]


8.3.4.2 Short-circuit testing

For the purposes of short-circuit testing, the transformer shall be magnetized between terminals A and B (30 kV) and the short-circuit performed with breakers between terminals B and 0 (15 kV). The test circuit shall be adjusted in such a way that the stationary short-circuit current is at least 6 kA r.m.s. in both windings. At the time of each connection, the duration of the short-circuit current shall be at least 300 ms (five periods at 16.7 Hz). The short-circuit test includes nine steps with a total of 50 operations in which the connection time point in each step is shifted in accordance with Tabell 3.

Tabell 3: Test sequence for the short-circuit test
Step no. Number of activations Angle at time of activation (º) <ref>This indicates the angle, calculated from the voltage's zero crossing, at which the short-circuit is to be provoked.</ref>
1 4 90
2 4 70
3 4 50
4 6 30
5 3 10
6 4 0
7 5 50
8 5 70
9 15 90


Following each step, a measurement of the transformer’s reactance shall be made in accordance with section Measurement and calculation of zero phase-sequence impedance. One condition for a satisfactory short-circuit test is that the transformer’s reactance following the entire test sequence shall not have changed by more than 2 %.

In cases where short-circuit impedance deviations are greater than 2 %, or where the short-circuit testing had to be discontinued for another reason, the transformer shall be dismantled bit by bit in the presence of the customer. The reason for any short-circuit impedance deviation shall then be investigated by the supplier and reported to the customer. Following this, the modified transformer shall be tested again in accordance with this section. Testing and modifications shall continue until the transformer has passed the tests.

In cases where short-circuit impedance deviations are less than 2 %, the transformer shall be lifted out of the vessel for inspection with the customer present. After that, routine testing according to section Routine tests shall be carried out again. After carried out and approved routine tests, the transformer is ready for delivery.

8.4 Testing of type-certified transformers

8.4.1 Routine tests

Routine testing of type-certified transformers includes all the routine tests listed in EN 60076-1, section 10, and PD measurements in accordance with EN 60076-3, section 12.2.2.


8.4.2 Oil samples in the testing room

The supplier shall, in the presence of the customer or the customer’s representative, take an oil sample from the transformer while it is inside the testing room. The sample shall be analyzed with a view to detecting the presence of PCBs and/or silicon, and the analysis shall be carried out by an accredited laboratory. The silicon content shall be measured using suitable techniques. The results of the test shall be included in the delivery. Samples must also be taken for corrosive test.

If agreed, other methods may be approved for verifying that the oil does not contain PCBs and/or silicon in accordance with the preceding paragraph.

If the test indicates the presence of PCBs (greater than 2 ppm) and/or silicon, the transformer must not be delivered to the customer.


8.4.3 Oil tests during the warranty period

Each year during the warranty period, the supplier shall, in the presence of the customer or the customer’s representative, carry out gas analyses in accordance with section Gas analysis and oil tests in accordance with section Oil analysis. The results of the analyses and tests shall be included in the delivery.

Different methods are required depending on whether the oil is filled up once and for all or not.


8.4.3.1 Gas analysis

Gas analysis shall be performed initially after three months of operation and thereafter every year and for the last time one month before the warranty inspection. The analysis shall be carried out by an accredited laboratory.


8.4.3.2 Oil analysis

Oil sample testing shall be performed initially after one year of operation and thereafter every year and the last time one month before the warranty inspection.

The sample analysis conducted one month before the warranty inspection shall also include detection of the presence of PCBs (more than 2 ppm) and/or silicon and shall be carried out by an accredited laboratory. The silicon content shall be measured using suitable techniques.


8.5 References

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9 MANUFACTURING INSPECTIONS

During the manufacturing of ordered transformers, the customer or the customer’s representatives shall be entitled to visit the factory whenever they wish.

On all visits to the factory, the customer or the customer’s representative shall be entitled to photograph the ordered transformers during the manufacturing process.

The supplier shall inform the customer, at least two weeks in advance, of the times of any inspections to be carried out in connection with the following manufacturing milestones:

  • All tank components on site at the factory
  • Windings ready for installation on the cores
  • Active components ready for placement into the vessels
  • Transformers ready for testing (routine testing of type-certified constructions or tests that are to be carried out prior to type certification)


10 TRANSPORT AND INSTALLATION OF TRANSFORMERS

10.1 Impact recorder

When transformers are being transported, an impact recor¬der shall always be mounted on the transformer. The impact recorder must not be of the mechanical type. The impact recorder shall be set to the correct time and date prior to transport. Downloading of the measurement results from the impact recorder shall always take place in the presence of the customer or the customer’s representative. The customer shall always receive a copy of the measurement results at the site in connection with the downloading.


10.2 Control schedule

In the course of construction reviews prior to type certification, a control schedule shall be drawn up and established.

This control schedule shall be followed for each transformer in the course of installation and commissioning.


10.3 Oil handling at the installation site

The transformer oil shall always be filled through a high-vacuum filter. Thereafter, the entire oil volume shall be filtered again at least once, so that the flash-over value is at least 60 kV/2.5 mm and the moisture content is below 10 ppm. A delivery certificate shall accompany the delivery.

The supplier shall, in the presence of the customer or the customer’s representative, take an oil sample from the transformer once final filtering is complete. The sample shall be analyzed with a view to detecting the presence of PCBs (greater than 2 ppm) and/or silicon, and the analysis shall be carried out by an accredited laboratory. The silicon content shall be measured using suitable techniques. The results of the test shall be included in the delivery. Samples must also be taken for corrosive test.


11 CHECKLIST

For each point in Tabell 4, the tenderer shall indicate whether the requirement has been satisfied. In the case of deviations from the stated requirements, the nature of and reason for each deviation shall be stated under the relevant point. Furthermore, the tenderer shall refer to the point in the tender document where it is shown that each requirement is or is not met. This checklist shall also be used at the time of delivery.

12 AIDS AND REFERENCES

12.1 Aids

Not relevant


12.2 References

This BVS refers to the following documents (if the EN, IEC and/or ISO documents exist as Swedish and/or Norwegian standards, the BVS refers to those):

BVS 543.14513 Teknisk specifikation för autotransformator 3/1.5 MVA och 5/2.5 MVA med byggnad för banmatning
EN 50163 Railway applications – Supply voltages of traction systems
EN 50180 Bushings above 1 kV up to 36 kV and from 250 A to 3.15 kA for liquid-filled transformers
EN 50329 Railway applications – Fixed installations – Traction transformers
EN 50388 Railway applications – Power supply and rolling stock – Technical criteria for the coordination between power supply (substation) and rolling stock to achieve interoperability
EN 60076-1 Power transformers – Part 1: General
EN 60076-2 Power transformers – Part 2: Temperature rise
EN 60076-3 Power transformers – Part 3: Insulation levels, dielectric tests and external clearances in air
EN 60076-10 Power transformers – Part 10: Determination of sound levels
IEC 60076-7 Power transformers – Part 7: Loading guide for oil-immersed power transformers
ISO 12944 Paints and varnishes – Corrosion protection of steel structures by protective paint systems