BS EN 60567:2011 pdf download
BS EN 60567:2011 pdf download.Oil-filled electrical equipment——Sampling of gases and analysis of free and dissolved gases——Guidance.
— a plastic three-way valve of standard type (7). modified to minimize dead volume by inserting pieces of stainless steel tubing (approximately 0,4 mm inner diameter (ID) and 1,5 mm outer diameter (OD)) into the inner branches and connected to a gas-injecting needle (10) (approximately 10 cm long, 0,25 mm OD) to go through the rubber septum into the oil flask (16),
— gas cylinders equipped with a pressure reducer and a valve (20).
NOTE 1 Qas cylend.rs containing each of Itt individual gases to be injected can be used, Ready-made
mIxture. 04 these gases can also be obtained from some gas auppliers
— a length of oil-resistant flexible tubing connecting the gas cylinder to the three-way valve (7) and Incorporating a hypodermic needle (approximately 0.3 mm ID and 0.6 mm 00). The latter acts as a leak to a water bubbler (21) whIch Is used to check the absence of back diffusion.
NOTE 2 Replace the length of tubing connecting ti gas cylinder to the three-way valv, after each gas
change.
The oil sampling system (Figures 4h to 4k) consists of glass syringes (19) of suitable capacity equipped with two three-way plastic valves (8)) and (9) and an oil-extracting needle (11) (approximately 0.8 mm ID. 1.0 mm OD and 120 mm long).
6.2,2 Procedure
NOTE Figures in brackets refer to those circled numbers in Figures 4a to 4k. The positions A to 0 of the threeway valves (7. 8 and 91 are illustrated In Figure 4d.
6.2.2.1 Degasslng the oil
a) Thoroughly clean all the glassware before assembling.
b) Secure the rubber septum and the flexible connections with pieces of twisted metal wire.
C) Clean. If necessary, approximately 1 I of mercury with pentane and filter through a finely pierced filter paper.
d) Adapt the oil reservoir (14). the splash bulb (15) and stopcocks (4) to the 5 I vessel (13). Connect the system to the vacuum pump (V) and evacuate the splash bulb (15) and the 5 I oil vessel (13) by opening stopcocks (2) and (4).
e) Fill the oil reservoir (14) with mineral insulating oil complying with IEC 60296 and allow oil to flow slowty through stopcock (3) into the 5 I vessel (13) until it is full, Then close the stopcock (2) and remove the oil reservoir (14) and the splash bulb.
NOTE If the procedure is followed carefully lr.lling time about 4 II) the oil itt the vessel wili be virtually gas-free.
1) Turn the oil vessel to bring it Into the position shown In Figure 4c. Place a wet cloth over It to prevent Its temperature rising and attach the mercury displacement system (17) to stopcock (1). Introduce 750 ml of mercury Into the system with stopcock (6) closed.
g) Connect the system to the vacuum (V). open the stopcock (5) and evacuate the section between stopcocks (1) and (6). Open the stopcock (6) to allow mercury to rise up to stopcocks (1) and (5). and then close stopcock (5). Raise the left bulb of the system (see Figure 7c) so that the mercury level is above the oil flask. Open the stopcock (1). Remove the wet cloth and switch on the magnetic stirrer (12).
6.2.2.2 Preparation of gas-in-oil standards See Figures 4c to 4g.
a) To inject the gases. attach the modified three-way valve (7), in position B, to the gas- injecting needle (10). Then push the needle through the rubber septum (16) into the oil. Turn the three-way valve to position 0 to purge the needle and valve with oil, then turn it to position B. Attach to valve (7) the barrel of a precision calibrated gas-tight syringe (18) of appropriate volume (precision within I %) and the gas cylinder connecting tubing (see Figure 4e). Allow a gentle flow of gas to flush the barrel, then slowly push the plunger several times into the barrel, finally down to the volume of gas to be injected, making sure there is continuous bubbling through the needle leak (21).
b) Switch valve (7) to the Injection position A, lower the mercury level below the needle tip, and push the plunger to inject the gas volume Into the oil. Switch valve (7) to position B and raise the left mercury bulb above the oil vessel.
C) Repeat the same procedure with each of the gases to be dissolved then remove the gas needle and valve (7).
When all the gases are dissolved, switch off the magnetic stirrer, Record the atmospheric pressure and temperature.
