Mastering HV Breaker Timing: ODES STR-F2 for Three-Phase Disagreement and Spring-Charging

Two “Small” Circuits That Decide HV Breaker Behaviour

In high-voltage circuit breaker control, two secondary circuits quietly determine whether the primary equipment behaves as designed:

• Three-phase disagreement supervision

• Spring-charging (energy-storage) motor control

If their timing is unstable, the result can be:

• Spurious three-phase disagreement alarms or trips caused by transient contact bounce

• Spring-charging motors running too long or starting simultaneously, stressing mechanisms and auxiliary power supplies

ODES’ STR-F2 time relay is designed as a “timing manager” for exactly these two circuits. With a simple operating principle – power-on delay, instantaneous reset on de-energisation – STR-F2 filters transient interference, stabilises decision criteria, and lets the breaker follow the intended operating sequence.

You can find more information on STR-F2 and related time relays at www.odes-electric.com.

Application 1 – Three-Phase Disagreement: Delay the Decision, Not the Protection

Three-phase disagreement supervision monitors whether all poles of a three-phase breaker reach the expected status (open/closed) within a defined time window. It is a key part of:

• Primary equipment interlocking

• Breaker failure logic

• Alarm and SCADA indication

The problem:

Auxiliary contacts and wiring in harsh environments can exhibit transient jitter at the instant of operation:

• Contact bounce on auxiliary switches

• Short-duration discrepancies between pole indications

• Control voltage perturbations during close or trip

If the scheme uses a “purely instantaneous” disagreement decision, these transients can trigger:

• Spurious three-phase disagreement alarms

• Unwanted trips or follow-up logic

STR-F2 solution:

STR-F2 is wired into the three-phase disagreement circuit with a short power-on delay:

• Operating mode: power-on delay, instantaneous reset on de-energisation

• When a disagreement condition appears, STR-F2 waits for a preset delay before operating its contacts.

• If the condition disappears within that delay (i.e., it was only transient jitter), STR-F2 does not operate.

Typical practice is to set the delay in the range of 2–3 seconds:

• Long enough to ride through transient discrepancies and contact bounce

• Short enough not to delay a genuine disagreement alarm in abnormal conditions

Result:

• The three-phase disagreement function becomes selective and stable, acting only on sustained conditions.

• Protection and interlocking logic operate according to a clear, time-filtered criterion, not momentary noise.

Application 2 – Spring-Charging Motor Control: Protecting the Mechanism and the Supply

Spring-charging (energy-storage) circuits supply the motor that charges the breaker operating mechanism. Their tasks include:

• Charging springs after a close operation

• Protecting the motor and mechanism from overrun

• Coordinating multiple motors to avoid simultaneous starts

Two typical challenges:

1. Over-run or blocked mechanisms

2. Multiple motors starting simultaneously

STR-F2 solution in spring-charging circuits:

• Charging timeout supervision

• Sequential motor starting

With a configurable range from seconds up to tens or hundreds of seconds, STR-F2 can be tuned to:

• Match the charging time characteristics of different breaker mechanisms

• Implement simple, robust sequencing for multiple energy-storage motors

How STR-F2 Works: “Power-On Delay, Instantaneous Return”

The operating philosophy of STR-F2 is intentionally simple and robust:

On energisation: delay before output operates

This is particularly suitable for circuits where:

• Only sustained conditions should cause action (e.g., confirmed disagreement)

• As soon as the input disappears, the timing must be cancelled without residual hold (e.g., charging command removed).

Key functional parameters:

• Operating mode

• Time setting ranges (two scales)

These two overlapping ranges allow engineers to cover:

• Fast transient filtering

• Medium-range sequence control

• Long-duration supervision tasks

Electrical Performance and Ratings

STR-F2 is engineered for secondary control in high-voltage environments.

Control voltage and operating range

• Available auxiliary/control supply options:

• Operate range: reliable delayed operation at approximately 55–65 % of rated control voltage (Un)

This ensures:

• Predictable timing even with typical DC or AC voltage variations

• Improved immunity to minor supply dips and ripple

Output contacts

• Two changeover contacts (2DPDT)

• Contact rating: 8 A at 250 V AC / 30 V DC

This contact set is sufficient for:

• Driving typical coils in primary control circuits

• Providing both control and indication/interlocking signals from a single device

Mechanical Design and Installation

STR-F2 is built as a compact module for dense panel layouts:

• Mounting: 35 mm DIN rail

• Width: 22.5 mm (narrow body for high-density installation)

• Terminals: screw terminals, recommended tightening torque 0.5 N·m

• Status indication: front LED for operating state

This allows:

• Easy integration into new and retrofit panels

• Clear visual indication for commissioning and maintenance technicians

Environmental and EMC Performance

High-voltage switchgear environments demand more than office-grade electronics. STR-F2 is specified for:

• Operating temperature: −25 °C to +70 °C

• Relative humidity: up to 95 % (non-condensing)

• Altitude: up to 4 500 m

EMC performance is designed for power industry conditions, including high levels of:

• Electrostatic discharge (ESD)

• Surge

• Fast transient burst

This makes STR-F2 suitable for use in:

• AIS and GIS switchgear control cabinets

• Hydropower plants

• Industrial high-voltage switchrooms

Implementation Guidelines for Protection and Primary Equipment Engineers

To use STR-F2 effectively in HV breaker control schemes:

1. Three-phase disagreement circuits

2. Spring-charging motor circuits

3. Contact allocation

4. Documentation and testing

Conclusion: A Dedicated “Timing Manager” for Two Critical HV Circuits

Three-phase disagreement supervision and spring-charging motor control are small parts of the schematic, but they have a disproportionate impact on breaker dependability and mechanism life.

The STR-F2 time relay provides a compact, engineering-grade way to manage timing in both circuits:

• Power-on delay, instantaneous reset behaviour tailored to disagreement and charging logic

• Two wide overlapping time ranges (0.05 s – 99.9 s and 0.05 s – 10 h)

• Multi-voltage AC/DC options with reliable operation from 55–65 % Un

• 2DPDT 8 A contacts, DIN-rail 22.5 mm housing, and power-industry EMC performance

By treating STR-F2 as a standard timing element for these two critical circuits, designers can improve selectivity, stability, and mechanism protection across high-voltage breaker fleets.

If you are designing or upgrading high-voltage breaker control schemes and need robust timing for three-phase disagreement and spring-charging circuits, ODES can help you consult on STR-F2 application, request typical wiring diagrams and setting guidelines, and learn how to standardise this relay across your switchgear projects.

To contact our engineering team for technical documentation or project support, please write to:

📩 tonyzhang@odes-electric.com

You can also learn more about ODES auxiliary relays and timing solutions at https://www.odes-electric.com/sales-page.

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