7/30/2019 Preliminary Progress 2

1/2

To: EETC - SZ

From: ZTZ-Service Co.

Subject: Preliminary Progress Report on Condition Assessment of 167 MVA

autotransformers 1T (3 phases) located at Cairo 500 kV S/S.

During period from February 24 to March 10 condition assessment of autotransformers

1T was carried out.

Brief scope of the works:

Autotransformers heating up to 60-65C; Water Heat Run Test; oil sampling from the

main tanks, diverter switches and bushings; measurements (on-load and at no-load) of

vibrations, magnetic field intensity, acoustic location of partial discharges; thermovision

inspection; measurements of the oil pumps and fans vibrations and currents; measurements

of tan, capacitance and insulation resistance of the main insulation and bushings;

measurements of no-load losses, impedances and windings DC resistances; oscillography of

the tap changers.

Regard to tests carried out on the autotransformers 1T (3 phases), the conclusions are:

Phase A (manuf. No. 69673)

Main insulation of the autotransformer and bushings insulation is in normal condition.Light OLTC contacts deterioration is presumed.It is possible a lightly loosening of pressure of the tapping and compensation windings

Tapping and compensation windings shall be pressed during repair.Also, a lightly loosening of pressure of the tapping core leg is possible.Pressure-gauges at the oil pumps No. 3 and 6 shall be replaced.At the coolers No. 1, 4 and 5 bearings of the upper fans shall be replaced.Lower fan at the cooler No. 4 shall be repaired.

Summary: autotransformer is in normal condition.

Phase B (manuf. No. 64458)

Main insulation of the autotransformer is in bad condition. Low level of the maininsulation resistance was fixed during condition assessment. Insulation contamination bypolar aging products presumed.

During repair insulation shall be washed with special oil by oil-spray method.Results of the insulation characteristics measurements testifies that all bushings are in

normal condition.Light OLTC contacts deterioration is presumed.Connections between LV bushings and LV leads shall be checked during repair.It is possible a lightly loosening of pressure of the windings and tapping core leg.

Windings shall be pressed during repair.Oil pump No. 7 shall be repaired. Pressure-gauge at the oil pump No. 6 shall be

replaced.At the cooler No. 7 bearings of the upper fan shall be replaced.

7/30/2019 Preliminary Progress 2

2/2

Summary: the main insulation of the autotransformer is in bad condition and shall betreated by oil-spray method during current year.

Phase C (manuf. No. 64459)

Main insulation of the autotransformer is in bad condition. Low level of the maininsulation resistance was fixed during condition assessment. Insulation contamination bypolar aging products presumed.

During repair insulation shall be washed with special oil by oil-spray method.Results of the insulation characteristics measurements testifies that all bushings are in

normal condition.Light OLTC contacts deterioration is presumed.It is possible a lightly loosening of pressure of the tapping and compensation windings.

Also, a lightly loosening of pressure of the tapping core leg is possible. Tapping andcompensation windings shall be pressed during repair.

Pressure-gauges at the oil pumps No. 1, 3 and 7 shall be replaced.

Summary: the main insulation of the autotransformer is in bad condition and shall betreated by oil-spray method during current year.

All defects can be eliminated during next schedule plan maintenance of the

autotransformers in the current year.

Manager of Transformers workshop

E. ABD EL AZIZ. El Sayed Salama

General Manager of Cairo 500 kV S/S

E. RAMADAN RAGAB

Head of North Sector

E. MOHAMED MAHFOUTH

Head of diagnostic departmentZTZ-Service Co.

Alexey A. Popov

DiagnosticianZTZ-Service Co.

Vladimyr V. Makolkin