Transformer Accessory Standards: JB/T, GB and IEC — How to Read a Tender Specification Before You Quote

Every few weeks we receive an enquiry that contains one spare line buried in a specification: “Gas relay: QJ4-80, conforming to [standard reference]”. That line decides more about price and delivery risk than the model number does. Here is how to read it.

1. Why the standard reference matters more than the product name

The model number tells you what physically arrives. The standard reference tells you what has to be proven on paper before it is accepted. Three practical consequences:

• It defines the tests. A standard states which type tests and routine tests apply, how they are performed, and against what limit values. Change the standard and you change the test programme.
• It defines the paperwork. Some references require a type test report from a recognised laboratory; others accept a manufacturer's declaration of conformity. Those are not interchangeable at review.
• It defines who pays when documents are rejected. Usually nobody — it becomes a delay.

In our experience the costly failures are rarely electrical. They are administrative: a certificate issued to a different model, a report older than the current edition, or a document that names a company the reviewing engineer cannot verify. That is why we read the standard reference with you at quotation stage on project packages, not after packing.

2. The naming systems you will meet

Chinese transformer designs and international tenders use different families of references. Knowing which family you are looking at tells you roughly how the numbers behave.

System	Issued by	Typically covers	Where you meet it
IEC (e.g. the IEC 60076 series for power transformers)	International Electrotechnical Commission	Transformer-level requirements: rating, temperature rise, dielectric tests, short-circuit withstand	International tenders, projects funded by multilateral lenders
GB / GB/T	Chinese national standardisation bodies	The Chinese national standard series — for example the GB 1094 series for power transformers, closely aligned with IEC 60076	Chinese domestic utility projects, Chinese OEM designs exported as complete units
JB/T	Chinese machinery industry	Component-level accessories — gas relays, pressure relief devices, valves, gauges — where no transformer-level standard exists	Accessory datasheets from Chinese manufacturers, replacement orders for Chinese-built units
DL/T	Chinese electric power industry	Operating, maintenance and testing practice for equipment in service	Utility O&M manuals, condition assessment procedures
IEEE / ANSI C57	US-based standards bodies	Widely used across North America and in markets built on US practice	Projects in North America and some regions of the Middle East
Manufacturer standard	The individual maker	Internal specification for one product family	Accessory datasheets — for example our QJ gas relay family is built to the manufacturing partner's standard Q/TTJ 32.07.11-2018

Read the reference exactly as printed. Do not convert it, and do not let anyone convert it for you verbally. A JB/T number and an IEC number describing the same component are not the same requirement — they can differ in the test method, the acceptance limit or the sampling rules, even when the physical part is identical.

3. “Equivalent to IEC” is a claim, not a property

You will see “IEC equivalent”, “as per IEC” or “type tested to IEC practice” in quotations. None of those phrases means anything by itself. Equivalence is demonstrated clause by clause and document by document:

• Name the standard, including the edition year (or the year of the referenced publication).
• State which clauses are claimed to be met.
• Point to the document that proves each claim: a type test report, a routine test record, or a design review.
• Confirm the scope of any referenced document covers the exact model being supplied — not only a similar product family.

If a supplier cannot produce the document named in their own claim, the claim costs nothing to make and nothing to accept. Ask for the scan before you approve the substitution.

4. Five checks before you accept, substitute or reject

1. Edition year. Standards are revised. A report issued against a withdrawn edition may still be technically valid and administratively useless. Always record the year.
2. Scope of the report. A type test report covers a design family and its ratings. Check that the supplied model, rating and construction fall inside that scope — particularly for sealed versus vented builds, which can sit under the same product family. See our sealed gas relay and standard QJ relay pages.
3. Test versus declaration. Know which one you are being offered. A manufacturer's routine test record and an independent type test report prove different things and are priced differently.
4. Who holds the certificate. Certificates attached to a trading company's letterhead usually originate from the actual manufacturer. Ask whose name appears on the certificate and whose scope it covers — that verification takes one email and prevents most document rejections.
5. The destination's own scheme. Local conformity programmes are additional to, not part of, the product standard. For example, shipments to Saudi Arabia may fall under the SABER route, handled by the importer with their customs broker against the HS code and the current technical regulation. This is arranged on the importing side; what we can do is supply the documents we hold and flag the requirement at quotation stage rather than at port.

5. The documents buyers ask for, and what each actually proves

Document	What it proves	When you need it
Type test report	The design was tested to the stated standard's method	New designs, first-time approvals, large tenders
Routine test record	The individual unit was tested before dispatch	Standard requirement on most orders
Certificate of conformity	Supplier declares the product meets the referenced standard	Submitting to the client's document file
Material certificate	Composition of pressure-retaining or sealing parts	Only if your specification asks for it
Quality system certificate of the manufacturing partner	The producer operates a documented, audited system — our partners are ISO 9001 certified	Supplier prequalification packs
Dimension / installation drawing	The part will physically fit	Any replacement order

Nobody needs all of these on every order. The mistake is discovering which ones you need after the goods are packed.

6. What to send us with your enquiry

To confirm a standard-related question quickly, send:

• The standard reference exactly as printed, including the edition year if the document shows one.
• The clause list, if the specification enumerates requirements.
• The model numbers you need to cover, and whether construction variants (for example sealed versus standard) are both in scope.
• The destination country and any local scheme you must register under.
• Whether documents need to be in English, and whether they go into a file that a third-party engineer will review.

With that, we can tell you — in writing, before you order — which of the above we can supply and which have to come from elsewhere. We do not guess at a standard number, and we do not issue a document that names a model it does not cover.

Related reading: Buchholz relay selection guide · How to read a transformer nameplate · How to choose a transformer accessories supplier