IEEE 1584 · Engineering

Ensure Rapid Fault Clearing With Relay Coordination Study

Prevent power outages and electrical hazards with proper relay coordination, customized to Vietnam standards. Carelabs builds the study from your facility's one-line diagram, modeling relays and breakers in ETAP to confirm each device trips only for the fault nearest to it.

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Selectivity is a production problem first

A fault on one machine that stops an entire building is not a protection curiosity. It is unplanned downtime, and on a shipping schedule that is the cost that gets noticed.

What We Deliver

What your relays are actually set to

Settings are read out of every device rather than copied from the settings schedule. On plants that have been extended more than once, the two disagree often enough that the audit alone changes the picture before any calculation is done.

WHAT WE FIND

The settings schedule is rarely the truth

Most sites can produce a protection settings schedule. Far fewer can produce one that matches the relays. Commissioning adjustments, vendor changes during extensions and undocumented temporary settings accumulate, and none of them reach the document.

As-found values recorded device by device before anything is proposed, which gives you a documented baseline even if no setting is ultimately changed.
Electronic trip units treated as relays, since adjustable LV units carry intentional delays that are frequently left at factory defaults nobody chose.
Instantaneous elements examined specifically, because an instantaneous set too low is the most common cause of a downstream fault taking the incomer.
Fuse and breaker combinations checked against the manufacturer's tested tables rather than against curve overlap alone, since cascade behaviour is not visible on a curve plot.
Any setting change presented with its effect on arc flash incident energy, so speed is never traded for selectivity without the exposure consequence being seen.

DELIVERABLES

What you receive

Issued against TCVN 7447 and the relay characteristics defined in IEC 60255, signed by the engineer who carried out the grading.

1As-found settings register covering every relay and adjustable trip unit on site
2Time-current curves per grading path with the achieved margin annotated at each level
3Discrimination register listing each failing pair and the fault current band where it fails
4Recommended settings in the entry format your devices use, ready to apply
5Earth fault grading treated separately, with pick-up and time multiplier per device

Reach Out

How the study runs

Read the installation

Every relay and trip unit is interrogated on site and the as-found values are recorded, together with CT ratios and the protection wiring as it is actually terminated.

Confirm the fault basis

Grading depends on fault current at each device position, so a verified short circuit basis is established first, either from an existing study or within this scope.

Model the devices

Manufacturer characteristics are built for every installed device, including the intentional delays configured into electronic trip units.

Test the discrimination

Each pair is examined across the full fault range rather than at a single value, since selectivity is commonly achieved at one current and lost at another.

Weigh speed against selectivity

Where the two conflict, options are put to your engineering and safety teams with the incident energy consequence attached to each, and the decision stays with you.

Apply and prove

Settings are issued for application with a verification checklist, so the values actually entered can afterwards be proven against the approved schedule.

Frequently asked questions

Almost always an upstream instantaneous element set low enough to see the downstream fault, so both devices operate together and the larger one wins. It is a settings problem rather than a hardware fault, and it is usually resolved by grading rather than by replacing anything, provided fault levels are known at each position.

That is the normal starting point and not an obstacle. The audit reads values out of the devices themselves, which produces the baseline the site never had. Sites that have been extended several times frequently have relays holding settings nobody on the current team chose, and documenting that is often the most useful part of the work.

Reading settings and verifying CTs is generally done with the plant running, and the analysis is offline. An outage is needed only where settings must be applied to devices that cannot be changed live, or where secondary injection testing is in scope. Any outage requirement is scoped and agreed before mobilisation.

Ideally yes, because they share inputs and pull in opposite directions. Clearing time governs incident energy, while grading margins tend to lengthen it. Running them against one model means the trade-off is resolved once, deliberately, rather than one study quietly undoing what the other recommended.

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