Protection
A timing test on a device 2 or device 62 relay measures how long the relay waits between its initiating condition and the change of its output contact. It confirms that the sequencing, permissive and protection delays in a scheme behave as the designer intended.
Device 2 is a time-delay starting or closing relay, and device 62 is a time-delay stopping or opening relay. Both appear in control and protection schemes to impose a deliberate wait: a starting sequence that must not begin instantly, a transfer or breaker-failure scheme that has to give the primary device time to act, or a motor-starting step that releases only after an interval. The timing test applies the initiating condition, which may be a control voltage, a contact closure or the removal of either, and measures the interval until the output contact changes state. The relay may be an electromechanical unit with a pneumatic or motor-driven mechanism, a solid-state timer, or a timing function inside a microprocessor-based protective relay. The test is a functional check of the relay itself and of the delay that the application depends on.
A delay that is too short lets a scheme act before the equipment it coordinates with has had time to respond, which causes nuisance operation, mis-sequenced starts or a transfer that closes onto a source that is not ready. A delay that is too long leaves an abnormal condition on the system or holds a process step back. Time-delay relays also drift. Pneumatic bellows wear, capacitors age, contacts pit, and a setting can change after a module is replaced or a settings file is loaded. Because the delay is rarely exercised in normal service, a timer that has failed or been mis-set can go unnoticed until the scheme is called on. Testing at acceptance proves the as-installed delay, and testing during maintenance finds drift before it matters.
A timing relay turns a deliberate interval into an output action. Electromechanical types create the interval with a pneumatic bleed orifice, a clockwork or motor-driven train, or a dashpot, and solid-state types count a clock or charge a resistor-capacitor network to a threshold. The two device numbers describe direction. Device 2 delays the starting or closing action after the initiating event, while device 62 delays the stopping or opening action after the event ends or reverses. The tester therefore needs a clean, repeatable starting event and a timer that begins at that instant and stops when the output contact changes, so that the measured interval is the relay's delay and not the test set's. Supply voltage, temperature and mechanical age all influence the delay of a real relay, so the conditions are part of the measurement. Many relays offer both on-delay and off-delay modes, and the mode must be known before the correct event is applied.
The relay is isolated from the trip and control circuits it normally drives, or those circuits are blocked, following the owner's lockout and work-permit procedures, so that a timing run cannot operate a breaker or start equipment. The instrument is a relay test set or a precision timer with a start input that follows the initiating event and a stop input that follows the output contact, wired so that contact bounce and wetting current are handled properly. The initiating condition is applied at the relay's rated control voltage, or through the logic input of a microprocessor-based unit, and the interval to the contact change is measured. The delay is checked at the field setting and, where the procedure calls for it, at other points of the adjustable range, with repeated runs to confirm that the result can be reproduced. For a device 62 relay the event is the removal or reversal of the initiating condition. The reading is taken as found before any adjustment and again after any adjustment. Afterward the circuits are restored and the setting is compared with the settings record.
The record holds the as-found delay measured on each run, the setting it was checked against, the mode of operation and which contact was timed, the control voltage and ambient temperature, and the identity and calibration status of the timer or test set. Any adjustment is noted together with the as-left result, and the relay identification and the scheme it serves are included so that the next test can reproduce the same arrangement.
The measured delay is judged against the setting specified for the scheme, with a tolerance taken from the manufacturer's data or from published tables, never from a single universal figure. Repeated runs should agree with one another, and a spread between runs points to a mechanical or component problem. Results are also compared with earlier tests of the same relay so that slow drift is noticed before the delay leaves its band. ANSI/NETA ATS-2025 covers acceptance testing of protective relays. Maintenance testing is covered in ANSI/NETA MTS-2023. Refer to your own licensed copies for the values and tolerances.
The equipment classes and standard sections that call for this test, and the UltraDb forms that carry it.
Device 2 delays a starting or closing action after the initiating event, and device 62 delays a stopping or opening action. Both are time-delay relays; which one a scheme uses depends on whether the wait applies when the signal arrives or when it ends.
A dial or software setting is only an intention. A timing test proves the delay that actually reaches the output contact, which wear, component aging, supply voltage or a mistaken adjustment can all change without any outward sign.
A precision timer with start and stop inputs is enough for simple on-delay and off-delay relays. A test set adds controlled voltage, current and logic inputs and makes microprocessor-based timers easier to exercise, but what matters is an accurate start and stop reference.
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