Pagkawas sa Langis sa IIEE-Business SF6 Density Relay: mga Kausaban ug Solusyon

1. Background

Ang mga aparato sa kuryente nga gigamit og SF6 gitawag na gamay sa mga kompanya sa kuryente ug industriya, naghatag og dako nga kontribusyon sa pag-unlad sa industriya sa kuryente. Ang pagseguro sa reliable ug safe nga operasyon sa mga aparato sa SF6 naging usa ka importante nga trabaho para sa departamento sa kuryente.

Ang medium sa pag-eliminate sa ark ug insulate sa mga aparato sa SF6 mao ang gas sa SF6, kini kinahanglan mobati og sealed—maski unsa nga pag-leak mag-compromise sa reliability ug safety sa aparato. Taliha, ang pag-monitor sa density sa gas sa SF6 mahimong importante.

Karon, ang mga mechanical pointer-type density relays kasagaran gigamit para moponitor sa density sa SF6. Kini nga mga relays maghatag og mga function sama sa alarm ug lockout kung adunay pag-leak sa gas, uban sa on-site density indication. Para mapadako ang shock resistance, kini nga mga relays kasagaran full sa silicone oil.

Pero, sa praktikal, kasagaran matagama ang oil leakage gikan sa SF6 gas density relays. Sumala sa industry reports ug feedback, kini nga problema widespread—tanang power supply bureau sa China nakasensya niini. Ang uban nga relays mogenerate og oil leaks sa less than one year sa operasyon. Ang problema nakakaapekto sa tanang manufacturers, sama sa imported ug domestic models. Sa short, ang oil leakage sa oil-filled density relays usa ka prevalent ug systemic issue.

2. Purpose of Filling with Silicone Oil

2.1 Improve Vibration Resistance
Ang mga density relays kasagaran gigamit og spiral spring (hairspring) type electrical contact. Bisag ang magnetic assistance mag-improve sa contact closure force, ang actual contact pressure (para sa alarm o lockout signals) gidepende sa weak force sa hairspring—even with magnetic assistance, maoy gamay ra. Taliha, ang contacts highly sensitive sa vibration.

2.2 Protect Contacts from Oxidation
Ang relay gigamit og magnetically assisted electrical contacts nga may low contact pressure. Sa panahon, ang oxidation makapudla og poor contact o complete signal failure. Ang filling sa silicone oil moguard sa air exposure, thereby protecting the contacts from oxidation ug ensuring long-term reliability.

3. Hazards of Oil Leakage

Hazard 1: Loss of Damping and Reduced Shock Resistance
Kung ang anti-vibration oil fully leak out, ang damping effect moguba, drastically reducing the relay’s vibration resistance. Under strong mechanical shocks during circuit breaker opening/closing operations, the relay may suffer from:

• Pointer jamming

• Permanent contact failure (stuck open or closed)

• Excessive measurement deviation

Hazard 2: Contact Oxidation and Contamination
Sa oil-leaked relays, ang magnetically assisted contacts exposed to air, making them prone to oxidation and dust accumulation. This leads to unreliable contact or complete signal interruption. If the density relay fails due to a stuck pointer or faulty contacts, it cannot detect actual SF6 gas loss.

Imagine an SF6 circuit breaker losing its insulating gas, yet the density relay fails to trigger alarm or lockout due to internal failure—and then attempts to interrupt fault current. The consequences could be catastrophic.

Additionally, leaked oil contaminates other switch components, attracts dust, and further compromises the safe operation of the SF6 switchgear.

4. Root Cause Analysis of Oil Leakage

Oil leakage primarily occurs at three locations:

4.1 Internal Leakage in the 7-Pin Terminal Box
Signal outputs from the relay require electrical connections from inside to outside the case, using a 7-pin plastic connector. The internal pins are made of copper, while the housing is plastic. The assembly is produced via overmolding (casting). Due to the different thermal expansion coefficients of metal and plastic, temperature fluctuations can create micro-cracks or gaps at the interface, leading to oil leakage.

4.2 Leakage at the Joint Between the 7-Pin Box and Case
This joint is sealed with an O-ring gasket. Under normal conditions, leakage is rare. However, when internal pressure increases or large temperature differences occur between inside and outside the case, stress on the seal can cause oil to leak from this joint.

4.3 Leakage at the Dial Cover
Leakage here is less common and usually results from improper assembly by the manufacturer, such as inadequate sealing or misalignment during production.