Проверка УЗО и RCBO в щитах KNX: ток срабатывания, время отключения и селективность

Настройка тестового прибора и подключения

Approved instruments:
  Fluke 1660 series (1662, 1664 FC) — recommended
  Megger MFT1741 / MFT1741+ — recommended
  Seaward Primetest 350 — suitable

Test lead connections:
  L (line) terminal   → line conductor at test point
  PE (earth) terminal → protective earth at test point
  Test point          → typically at socket outlet or
                        load terminal of RCBO

Critical: always test from the FURTHEST POINT of the
circuit (highest earth fault loop impedance Zs) — this
is the worst-case condition for RCD operation.

RCD test mode selection:
  0°  phase angle: positive half-cycle injection (standard)
  180° phase angle: negative half-cycle injection
  BS 7671 requires testing at BOTH phase angles for
  Type A RCDs — some may exhibit different trip times
  depending on fault current waveform phase

Последовательность тестов УЗО и критерии прохождения

Test 1 — Half rated current (I△n / 2):
  30mA RCD: inject 15mA
  100mA RCD: inject 50mA
  Pass criterion: NO TRIP in 300ms
  Purpose: verify RCD does not nuisance trip below threshold

Test 2 — Rated current (I△n):
  30mA RCD: inject 30mA → trip in ≤ 300ms
  100mA RCD: inject 100mA → trip in ≤ 300ms
  Pass criterion: TRIP within 300ms
  Record measured trip time (e.g. 42ms)

Test 3 — Five times rated current (5 × I△n):
  30mA RCD: inject 150mA → trip in ≤ 40ms
  100mA RCD: inject 500mA → trip in ≤ 40ms
  Pass criterion: TRIP within 40ms
  Purpose: verify fast clearance for high earth fault currents

Test 4 — Mechanical test button:
  Press test button on RCD face
  Pass criterion: RCD trips and latches open
  Purpose: verify mechanical trip mechanism operable

S-type (time-delayed) RCDs — additional criteria:
  Rated current test: trip time between 130ms and 500ms
  (IEC 61008-1 for S-type RCCBs)
  Ensures S-type clears AFTER standard 30mA RCDs downstream

Проектирование и проверка селективности УЗО

Selective (S-type) design:
  Upstream: 100mA S-type RCCB (time delay 200–300ms)
  Downstream: 30mA standard RCCBs / RCBOs

Selectivity verification test:
  Step 1: Induce 30mA earth fault on a downstream circuit
  Expected: only the downstream 30mA RCBO trips
  Upstream 100mA S-type remains closed
  → Test PASS if only downstream device trips

  Step 2: Induce 100mA fault (via instrument 5×I△n on 30mA RCD)
  Expected: both downstream 30mA RCBO AND upstream S-type trip
  (selective discrimination breaks down at 100mA — both trip)
  → This is acceptable and expected behaviour

  Step 3: Reset downstream RCD, verify upstream S-type reset
  Expected: both reset and circuit restored normally

Selectivity NOT achieved if:
  Upstream S-type trips during 30mA downstream fault
  → cause: S-type has too short a delay or incorrect type
  → remedy: verify S-type is IEC 61008-1 S-classified device

Причины и способы предотвращения ложных срабатываний

Root cause:
  KNX PS640 input capacitance: typically 400µF per TP segment
  On power-up: capacitor charges from mains → brief current spike
  Spike has DC component → Type AC RCD cannot discriminate
  Type A RCD detects DC component → may trip at inrush peak

Mitigation 1: Use Type A RCDs (not Type AC)
  Type A RCDs have higher immunity to capacitive inrush
  compared to Type AC which is sensitive to DC components

Mitigation 2: Interlock relay to sequence KNX PS640 startup
  Delay KNX PS640 energisation by 500ms after main RCD
  settles (use time-delay relay or KNX relay with startup delay)
  By the time PS640 energises, RCD has stabilised

Mitigation 3: Omit 30mA RCCB on KNX PS640 circuit
  Where nuisance tripping persists despite Type A RCDs:
  Install upstream 100mA fire protection RCCB only
  KNX bus cable (YCYM 2×2×0.8mm²) is Class II insulated
  SELV bus voltage (29V DC) — Class II cable provides
  equivalent shock protection for the bus conductors
  (Note: 230V output circuits from KNX actuators still
  need standard 30mA RCBO protection)

Mitigation 4: Electromechanical RCBO for PS640 circuit
  Electromechanical type has longer time constant
  Less sensitive to capacitive transient peaks

Протокол результатов испытаний — раздел УЗО

For each RCD / RCBO — record:
  Circuit reference (from circuit schedule)
  RCD type: AC / A / F / B
  Rated residual operating current I△n (mA): 30 / 100 / 300
  I△n/2 test result: NO TRIP in 300ms — PASS / FAIL
  I△n trip time (ms): measured value, e.g. "42ms"
  5×I△n trip time (ms): measured value, e.g. "18ms"
  Test button mechanical trip: PASS / FAIL
  Phase angle tested: 0° and 180° (for Type A)
  Overall result: PASS / FAIL

S-type RCDs — additional columns:
  S-type delay trip time at I△n (ms): e.g. "245ms"
  S-type non-trip at 50mA (15ms): PASS / FAIL

Format: IEC 60364-6 Annex C (or BS 7671 equivalent)
Retention: minimum 10 years (commercial), life of installation (residential)
Provided to: building owner, local authority (if required), insurer