Free Tool · IEEE C37.06 / C62.22 · Temporary Overvoltage · Cross-Discipline

Temporary Overvoltage Study

Breaker outrush current and arrester energy duty verification per IEEE C37.06 and IEEE C62.22. Checks MCOV/TOV adequacy, inrush/outrush current limits (C0/C1/C2 class), and cap-bank energization transients. Cross-discipline — applicable to any system with capacitor banks or switching transients.

System Parameters
Surge Arrester
Feeder Breaker
Capacitor Bank
Back-to-Back Switching
For mutual inrush frequency calc
Mutual inrush L for back-to-back
Optional outrush damping
Outrush + Equipment Checks
Validates cap bank outrush against breaker class limits and equipment rating.
Breaker Restrike — Arrester Energy Duty
IEEE C62.22 §7.3 — Energy injected into arrester during breaker restrike with capacitor bank load. E = 0.5 × C × V²
Line-to-line voltage at restrike
Bank capacitance for restrike energy
Manufacturer's energy rating
TOV Study Results
1. Arrester MCOV/TOV Verification
2. Arrester Energy — Breaker Opening
3. Arrester Energy — 1LG Fault
4. Cap Bank De-energization (Restrike)
5. Inrush Current — Back-to-Back Switching
6. Outrush Current — Fault Condition
7. Transient Overvoltage — Cap Bank Energization
Export TOV study report
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Worked Example — 15 kV / 25 MVAR / C1 class
FAIL IEEE C37.06 / C62.22 TOV Study — 15 kV system
MCOV ratio (provided / required)1.455
Energy — breaker opening (kJ)19091.883 kJ
Energy — 1LG fault (kJ)114551.299 kJ
Outrush current (kA)30 kA
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FAQ

What is the difference between C0, C1, and C2 breaker classes per IEEE C37.06?
IEEE C37.06 classifies switchgear by outrush current capability during capacitor bank switching. C0 (standard) requires Peak I_o < lesser of 50 kA and 1.41 x I_sc_rated — no additional margin. C1 (distribution) and C2 (heavy-duty) require Peak I_o < 2.6 x I_sc_interrupting with >=15% margin. The class must be proven by the breaker manufacturer through type tests; C0 is the default if no documentation is provided.
How does a surge arrester protect against TOV events?
Metal-oxide varistor (MOV) arresters clamp TOV by shunting surge energy to ground. The arrester's MCOV (maximum continuous operating voltage) is the RMS voltage it can continuously withstand. The arrester's TOV capability (kV) specifies how much overvoltage the arrester can withstand for a given duration without failing. During a breaker opening event, the arrester absorbs energy E = V_peak x I_fault x t_duration (IEEE C62.22 Eq. E1/E2).
When are capacitor bank switching events omitted from the TOV study?
The cap-bank switching sections (inrush current, restrike energy, and energization TOV) are automatically omitted when the capacitor bank toggle is set to 'No cap bank in project'. The remaining checks (arrester MCOV/TOV, breaker opening energy, SLG fault energy, and outrush current) always run regardless of this toggle.
What should I do when the TLI recommendation is flagged?
A TLI (Transformer-Limited Interface) flag means the outrush current exceeds the breaker's rating for its class. Recommended actions: (1) verify upstream transformer impedance, (2) add a current-limiting reactor in series with the cap bank, (3) relocate the cap bank to a location with higher source impedance, or (4) upgrade the breaker to a higher class (C1 or C2).