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The Ultimate Guide to Dead Front Transformer

Dead Front Transformer (1)

Dead front transformer that we know more is dead front pad mount transformer, this type of power transformer is widely used in North American market. Daelim can manufacture but dead front also live front dead mount transformer based on IEEE/ CSA standards and provide the transformer under your requirements.

Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Oil immersed transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva

Table of Content

What is a dead front transformer?

Usually, 6 or 3 units single-way or dual-way high voltage bushing are used for dead front transformer.The high voltage bushing of the dead front transformer is fully insulated.

And usually the 200A double way connector this product is mainly used for pad mounted transformer, outdoor loop feed switchgear and other high voltage electrical equipment.

The commonly used accessories are: elbow connectors, elbow lightning arrester and bushing well.

15kV 200A double way bushing, connected to the bushing well to achieve single and double conversion.

One way has similar functions with the single bushing, and the other way is connected to the elbow arrester (improve overvoltage protection), or change the wiring mode of the pad mount transformer.

The dead front transformer 200A double way bushing adopts high quality EPDM rubber insulation, and the advanced structural design inside the double way bushing ensures the normal fire arc when disconnected from the elbow joint.

The unique anti-reverse design ensures that the double-pass sleeve joint rotates to a suitable installation position without affecting the connection performance.

The dead front transformer 200A double-pass socket joint European front joint, European-type rear joint, European-type rear-connection lightning arrester, Elbow-type cable head, The T-type head, Shielded cable joints, etc.;

One-piece casing has a docking casing, 202 Tubes, 235 Tube sleeve, etc.; The terminal head has cold shrink accessories, Cross-linking of heat-shrink accessories; DFW electrical branch box, SF6 switchgear and other accessories,

The tors are made of high insulation imported rubber, Through the multilayer composite injection process of fully automatic rubber injection equipment, non-toxic, tasteless;

Internal 100% pure purple copper; The stress cone in the lower part evenly cuts the electric field by the external screen disease of the cable terminal: the screen pattern in the upper part seals the live part,

The outer surface has a semi-conductive screen salary layer, The external surface is ground, Can operate safely in the water, Easy to install, long life characteristics, Can completely replace the imported products.

The casing is made of epoxy resin, mainly used for cable connection box ring network switch cabinet, with good mechanical performance and electrical performance.

What are the types of dead front transformers?

Single-phase and three-phase transformer

Dead front ransformers can be divided into single-phase and three-phase according to the number of phases.

Generally, the capacity of single-phase dead front transformer is much smaller than that of three-phase, and the volume and weight are also much smaller.

The single-phase transformer capacities designed and produced by Daelim are: 15kVA, 25kVA, 37.5kVA, 50kVA, 75kVA, 100kVA, 167kVA, 250kVA,can be fully compliant with ANSI DOE IEEE CSA and IEC standards.

Three-phase dead front transformer capacity is more, such as 500kVA, 1000kVA, 1500kVA, 2000kVA, 2500kVA, 3000kVA, 4000kVA, 5000kVA, etc., the maximum can be 10MVA.Daelim can be fully compliant with ANSI DOE IEEE CSA and IEC standards, and has ul certificate and ul listed.

Loop feed transformer and radial feed transformer

Dead front transformer according to user needs, there are two types: Loop feed transformer and radial feed transformer.

Loop feed transformer is a transformer with 6 high voltage bushings. Three of the high-voltage bushings can be connected to other transformers for looping out. Used in the ring network circuit, it can be led out by two routes, which can ensure that the normal equipment is supplied with power when some equipment is abnormal.

Radial feed transformer is a transformer with 3 high voltage bushings. There is only one line leading out, which is used in the terminal line, and can only be connected to the power supply equipment. Once the transformer is abnormal, it will affect the normal power supply of the equipment.

In Daelim’s dead front transformer project, the type that customers choose more is loop feed transformer.

What is the difference between live front and dead front transformers?

As I mentioned at the beginning of this article, the live front and dead front are terms that typically used in oil immersed pad mounted transformers. Usually your requirement of high voltage is the dead front or live front.

We will according this requirement to design different drawing and products for single phase pad mount transformer and three phase pad mount transformer.

Live front high voltage terminations we can see that cable and terminal are exposed outside. The high voltage bushing of the Live front transformer is not fully insulated. For instance, the cable will be stripped at the end and inserted into an eyebolt terminal of a porcelain or a composite bushing.Touching the live front bushing may cause electric shock when current is flowing.

Dead front high voltage terminations we can found there is the elbow connector that connect to the bushing well installed on the pad mount transformer.The full set of accessories including a bushing well, loadbreak insert, and a loadbreak elbow.The high-voltage bushing of the Dead front transformer is fully insulated, so when you open the front compartment to operate, it will reduce the safety risk.

To sum up, the biggest difference between the Dead front transformer and the live front transformer is the structure of the high-voltage bushing. The high-voltage bushing of the dead front transformer is fully insulated, and the high-voltage bushing of the live front transformer is exposed to the outside and is not completely insulated. Therefore, Dead front transformer is safer than live front transformer.

Dead Front Transformer (2)

What are the CSA standard specifications of the dead front transformer?

Three-phase, pad-mounted distribution transformers with separable insulated high-voltage connectors which means dead front pad mount transformer comply with the CSA C227.4-06 standards.

Dimensions: all transformers shall have the dimensions shown in Table 8.

Transformer tank: the transformer shall have sufficient strength to withstand a minimum gauge pressure of 50 kPa, without leakage or permanent distortion of the tank exceeding 0.25% of the diagonal dimension of the surface so affected.

The transformer base shall be arranged so that the tank bottom does not touch the pad.

Lifting provisions: construction of the unit shall be such that it can be lifted, tied down during shipment, skidded, or slid into place on the mounting pad without disturbing high- or low-voltage cables.

Jacking and lifting provisions shall be arranged on the tank so as to prevent overturning when lifted.

Jacking provision: jack steps or equivalent jacking facilities shall be provided on the tank. Vertical clearance for a jack shall be 150 mm minimum and 165 mm maximum.

Transformer base: the transformer base of units rated 750 kV•A and larger shall be arranged for rolling in four directions, parallel to and at right angles to one side of the transformer.

High-voltage bushing wells: with a removable stud shall be provided for connection to the distribution system through separable insulated connectors for dead-front operation and shall meet the dimensional and electrical requirements of IEEE 386.

The minimum continuous and short-circuit current-carrying capabilities of components for looped primary cable systems shall be 200 A rms continuous and 3500 A rms symmetrical, 3 s. Each high-voltage bushing well shall be equipped and shipped with a protective cap.

Low-voltage terminals: for all sizes of transformers shall be the spade type in accordance with Table 9 and Figure 11 and shall have a thickness that will provide adequate ampacity.

Terminals shall be of plated corrosion-resistant metal, suitable for use with copper or aluminum connectors. Low-voltage terminals for stud-type bushings shall be of plated copper suitable for use with copper or aluminum connectors.

Routine tests: the tests specified in Items (a) to (h) of this Clause shall be performed as routine tests on all transformers, but not necessarily in the sequence given:

(a) ratio on each connection;

(b) angular displacement;

(c) no-load losses at 105% rated voltage;

(d) exciting current at 105% rated voltage;

(e) load losses and impedance at rated current, on the rated voltage connection, corrected to 85 °C. This test shall be performed on the high-voltage connection that has the highest measured loss value;

(f) applied voltage;

(g) induced voltage; and

(h) transformer tank leak-detection test. This test shall be performed on each transformer tank to verify the integrity of the welds and on the final assembled unit without the pressure relief device.

A test report certified by the manufacturer, acknowledging that all routine tests have been performed, documenting energy efficiency according to CAN/CSA-C802.1 and the results of the tests specified in Items (c), (d), and (e), and signed by a professional engineer or otherwise authorized person, shall be submitted to the purchaser for each manufacturing lot.

Daelim’s dead front transformers have been in the Canadian market for four years, and the team is very proficient in Canadian technical standards. In the past four years, we have helped customers successfully solve many technical problems. If you happen to have Canada’s pad mounted transformer needs, don’t hesitate to contact Daelim immediately.

Try for free information about the power transformer specification for tender in Canada

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About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.