Why use the selected device documentation?
Schneider Electric's US polarity FAQ, modified 1 June 2026, discusses markings such as H1 and X1 in its equipment context and directs qualified personnel to the appropriate CT installation guide. It also warns of hazards involving open CT secondary circuits. This is a reason to use controlled manufacturer evidence, not to treat this page as wiring instructions.
Substation Drafting is independent and is not affiliated with Schneider Electric. Only qualified authorised personnel perform actual electrical work under approved procedures. Engineering sign-off is performed only by the registered engineer on the job.
Sources: Schneider Electric: Current transformer polarity FAQ, modified 1 June 2026
Which references should be compared?
Start with the equipment schedule, selected CT guide and approved design drawings. Do not assume wire colour, terminal naming or polarity notation is universal across products.
| Evidence | Record | Cross-check |
|---|---|---|
| Selected device | Model, ratio schedule reference and guide revision | Guide applies to the scheduled device |
| Physical marking | Exact marking from approved equipment evidence | No label inferred from a different product |
| Schematic convention | Symbol, polarity notation and legend reference | Designer's convention is explicit |
| Circuit identity | CT core and circuit identifiers | Same core is followed across drawings |
| Terminal reference | Controlled terminal schedule and drawing revision | Identifiers resolve without an assumed rename |
| Discrepancy | Both source references and unresolved question | Authorised technical owner gives the disposition |
| Closure | Approved revision and reviewer reference | The evidence chain is rechecked after change |
How can a drawing trace fail?
Illustrative example. A fictional equipment schedule identifies CT-DEMO core 1. The schematic uses that core identifier, but a terminal schedule labels the circuit only CT-DEMO, with no core reference. The reviewer cannot establish the intended core from the terminal record alone. Record the missing identity link and route it to the designer.
Do not solve the ambiguity by copying a polarity mark from an adjacent core or by assuming the first listed terminal belongs to core 1. The drawing owner must supply the approved mapping and any associated design change.
After the response, check that the device, core, circuit and terminal identifiers remain aligned across the revised records. A corrected terminal label does not establish that the entire protection circuit has been tested.
What should the drawing reviewer avoid claiming?
This worksheet does not verify actual installed polarity, protection performance or commissioning results. Those require their own authorised procedures and technical evidence. Record which task the documentation review covers and which tests remain separate.
Keep the approved manufacturer guide revision with the drawing issue record. If equipment selection changes, reopen the device-specific checks. Do not rely on memory of another CT model to approve the new convention.
Close each discrepancy against the actual approved drawing revision. Preserve the original question and response so later reviewers can understand why a symbol or identifier changed. No site operation or live secondary-circuit work is authorised by this guide.
Common questions
What else should the bid team know?
Are CT polarity labels identical on every product?
Do not assume that. Use the selected device documentation and approved design convention.
Does a completed drawing trace prove installed polarity?
No. Installation and test evidence are separate authorised checks.
Can a missing core identifier be inferred from drawing order?
No. Request the approved mapping and retain the discrepancy until resolved.
Primary sources
- Current transformer polarity FAQ, modified 1 June 2026Schneider Electric