Lubrication of Circuit Breaker Mechanisms 1 What is

Lubrication of Circuit Breaker Mechanisms 1

What is different about circuit breaker lubrication? Many of the same components as other industries, but they do not operate in the same way • Long periods of inactivity • Large temperature swings • Outdoor exposure • Much longer service intervals • Wear is not usually an issue © 2015 Doble Engineering Company. All Rights Reserved 2

Lubrication issues for MV circuit breakers Greases harden - do not have adequate life for typical CB maintenance intervals No zerk fittings – lubrication is difficult Oils deteriorate – chemical reaction with moisture, oxygen and heat Labor intensive – requires major disassembly to maintain Result – slow trips and no recloses; burned coils and motors This oxidized and hardened grease no longer has lubricant in the thickener © 2015 Doble Engineering Company. All Rights Reserved 3

What is grease Grease is a fluid lubricant (oil) mixed with a thickener. It often contains additives to give it special performance characteristics © 2015 Doble Engineering Company. All Rights Reserved 4

Types of oils and greases Petroleum Oils (Mineral Oils) • Made from paraffinic or naphthenic oils • Complex mixture of different crude oils • Little control over molecular structure means variation of lubricating properties Synthetic Oils – many unique names Manufactured from few raw material components • Desired lubricant properties can be controlled • PAO is acronym for polyalphaolifin: very good lubricating properties; suitable for many bearing, bushing and moving contact applications • Ester oils have polarity that attracts them to steel bearing surfaces: very good lubricating properties; moisture can be absorbed over time, which 5 © 2015 Doble Engineering Company. All Rights Reserved degrades them

Types of oils and greases Silicone oils • Usually have very good oxidation and evaporation properties: good choice for low temperature, moderate load, long life applications • Applications include moving switch contacts • Compatible with many plastic materials. . Fluorosilicone oils • Excellent resistance to oxidation, evaporation and wash-out from water or chemicals such as degreasers and penetrants © 2015 Doble Engineering Company. All Rights Reserved 6

The components of grease Grease Thickeners are classified as soap or non-soap • Soap thickeners include aluminum, calcium, sodium and lithium • Non-soap thickeners include silica gel, clay, urea and PTFE Soap thickener can be combined with other materials to raise the temperature at which the grease liquefies. The greases made with these enhanced thickeners are called complex greases. Thickeners are used to make the lubricating fluid semi-solid so it does not flow out of tight spaces. Additives Mostly used to enhance properties of the base oils • Antioxidants • Corrosion inhibitors • Anti-wear © 2015 Doble Engineering Company. All Rights • Viscosity stabilizers 7 Reserved

Selection of grease 1. Remove old grease or be aware of thickener compatibility 2. Consider low temperature performance and other environmental factors 3. Choose a synthetic grease. There is no advantage of petroleum base grease for circuit breaker applications. What life do you want? 4. Select a grease with base oil that resists oxidation. This is key to long, satisfactory performance. Synthetic oils have much better oxidation characteristics than petroleum oils because of the control of properties during manufacturing. PAO and ester oils, except for the low molecular weight oils, have both good oxidation and good evaporation characteristics. Silicone and fluorosilicone oils used in greases have even better oxidation and evaporation properties, resulting in longer life. © 2015 Doble Engineering Company. All Rights Reserved 8

New methods: Materials § Fluorosilicone oil. It is thin enough to penetrate tight clearances, evaporates very slowly and does not oxidize. It is a good lubricant and has long life. § Fluorosilicone grease (eg. Dow 3451 grease) is used where parts can be reached. 9 © 2016 Electric Power Research Institute, Inc. All rights reserved.

Basics Yearly Exercise During preventative maintenance Rejuvenate grease with a compatible oil. Lubricate all pivot points with oil , in various positions during maintenance charged / discharged / open / closed. Clean old grease off and apply new grease lightly. Never use aerosol penetrating solvents they are temporary and dry out any remaining oil in the grease. Upgrade to longer lasting grease during overhaul activities. 10 © 2016 Electric Power Research Institute, Inc. All rights reserved.