IR SA Case Study

Monit ori oring ng of Surg urge e Arr Arre est ers t hroug hrough h Thermographi Thermographic c Ins Inspec pectt ion –  Case St ud udii es Tereza Cristina Leite Galindo  Compa ompanhi nhiaa hidroelét hid roelétririca ca do São São Francisco – Chesf  Chesf  Participants: Adolpho Calazans, Augusto Miranda, Eduardo Luiz, Esdras Rodrigues, João Domingos, Josué Beltrão, Max Norat, Marcos Venício, Companhia hidroelétrica do São Francisco - Chesf 

ABSTRACT In this paper we present evaluation cases of surge arrester operational conditions, through thermographic inspections, criteria applied in the field, and analysis carried out in units removed from operation due to the problems indicated by thermograms. INTRODUCTION Chesf (Companhia hidroelétrica do São Francisco) has been applying the thermographic inspection technique in its substations for more than 30 years, initially in connections and later for equipment evaluation, including surge arresters.

The methodology applied for the surge arrester inspection is based on a structure of possibilities from two types of evaluations:

• • •

Quantitative evaluation – considers the difference between the absolute temperature of the object and the room temperature of the same; Comparative evaluation – considers the temperature difference between si milar surge arresters.

The numeric criteria are established from the evaluations according to the table below: Ligntening

Normal (∆T °C) Comparative ≤ 3 Quantitative ≤ 5

Critical Level 1 Critical Level 2 (∆T °C) (∆T °C) >7 3 < ∆T ≤ 7 5 < ∆T ≤ 10 > 10

DEVELOPMENT Some samples were selected to better analyze the applied criteria and the errors associated to the measuring process in the field:

• •

To carry out laboratory analyses after field i ntervention; To monitor the field work through interventions of porcelain surface cleaning.

The following case studies give examples of our work. Units taken to the laboratory: Case 1:

230 kV Surge Arrester.Substation: MRR Description of occurrence: Inspection in 04/19/05, at 18:45h. Room temperature of 29 oC and relative humidity of 73 %. Thermal critical state level 2. Action: removal of operation equipment. Thermogram carried out in the field during inspection:

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

49,8°C J6: 41,9°C 40 30 20 17,9°C Figure 1. Thermogram of surge arrester in critical condition 

Laboratory analyses:

• •

Measurement of losses – it wasn’t possible to carry out this analysis due to the instability at the measuring bridge, indicator of high losses; Measurement of leakage current:

Tension (kV)

1ª. Reading

2ª. Reading

3ª. Reading

I (µA)

I (µA)

I (µA)

2.5

84.7

87.4

88.9

5.0

58.1

53.4

46.8

It was not possible to progress with the leakage current measurer due to high current indication.

Figure 2. Opening of the unit.

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

Case 2:

230 kV Surge Arrester. Substation: MSD Description of occurrence: Inspection in 04/02/05, at 22:15h. Room temperature of 25 oC and relative humidity of 96 %. Thermal critical state level 2. Action: removal of operation equipment

45,8°C ase A*: 33,3°C 40

30

20 17,1°C Figure 3. Thermogram carried out in the field during  inspection indicating significant problem.

Laboratory analyses:

•

Measurement of leakage current and dielectric losses. It was not possible to carry out the analyses due to high losses.

Internal Corrosion

Figure 4. Opening of the unit.

InfraMation 2006 Proceedings

Figure 4b. Internal Corrosion.

ITC 115 A 2006-05-22

Case 3:

230 kV Surge Arrester. Substation: PRD Description of occurrence: Inspection in 12/18/01, at 19:00h. Room temperature of 22 oC and relative humidity of 74 %. Inspection in 01/15/2002, at 21:00h. Relative humidity of 73 %. Thermal critical state level 2. Action: removal of operation equipment Thermograms carried out in the field during inspections:

32,7°C

18-12-2001

15-01-2002 - 28 dias após a ins A: 45,8°C

43,3°C 40

30 30

A: 24,9°C

25 20 21,2°C

Figure 5. Thermogram of problem arrester

16,9°C

Figure 5b. Thermogram of critical problem arrester 

Laboratory analyses:

•

Measurement of leakage current:

Superior Section: Voltage Current (kV) IP-P IP÷√2 3° h 5° h 7° h (mA) (mA) (%I60Hz) (%I60Hz) (%I60Hz) 2.5 5 10 20 30 40 50 60 70 80 90 100 105

0.18 0.32 0.61 1.20 1.72 2.24 2.72 3.24 3.72 4.28 5.28 9.40 14.6

0.06 0.11 0.21 0.42 0.60 0.79 0.96 1.14 1.31 1.51 1.86 3.32 5.16

0.00 0.00 0.00 1.28 1.69 1.31 1.54 1.36 3.42 7.57 15.05 26.87 32.96

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.21 5.10 10.97 14.13

InfraMation 2006 Proceedings

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.28 3.29 3.46

ITC 115 A 2006-05-22

Inferior Section: Voltage Current (kV) IP-P IP÷√2 (mA) (mA)

3° h 5° h 7° h (%I60Hz) (%I60Hz) (%I60Hz)

2 5 7 10 12 15 17 20 25

0.00 0.00 0.00 0.44 0.47 0.22 0.00 0.84 2.68

2.5 6.5 9.8 13.8 16.0 20.0 21.2 29.2 40.0

0.88 2.30 3.46 4.88 5.65 7.07 7.50 10.32 14.14

0.00 0.00 0.00 0.00 0.00 0.15 0.14 0.52 0.84

1.79 2.08 2.32 2.18 2.46 3.29 4.21 5.79 7.61

What became evident was the inferior section deteriorated faster with the increase of the losses, in comparison with the superior section.

Figure 6. Opening of the inferior unit.

Figure 6b. Bottom of inferior unit.

Case 4: 230 kV Surge Arrester. Substation: MSD Description of occurrence: Inspection in 11/09/2005, at 19:20h. Room temperature of 29 oC and relative humidity of 72 %. Thermal critical state level 1. Action: removal of operation equipment. Thermograms carried out in the field during inspections:

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

Lado NORTE

40,2°C 40

Lado SUL

30

40,2°C 40

30 B*: 32,7°C

Ø B1: 33,5°C

20

20

18,3°C

18,3°C

Figure 7. Thermogram of problem arrester, north side 

Figure 7b. Thermogram of problem arrester, south  side 

Laboratory analyses:

•

Voltage (kV)

Measurement of leakage current and dielectric losses: Superior Section 2

Inferior Section -1

10

Leakage Leakage Current Dielectric Current Dielectric (mA) Loss (W) (mA) Loss (W) 2.37 0.3481 4.60 0.6204

20 30

6.70 26.63

1.3934 3.1751

9.90 23.90

2.6058 5.9656

40

37.83

6.0296

52.40

10.9255

50 60

70.20 111.70

9.2001

95.00 167.00

18.5763

70

208.30

350.00

Figure 8. Opening of the inferior unit.

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

Case 5: 230 kV Surge Arrester. Substation: PRD Description of occurrence: Inspection in 09/28/2005, at 19:14h. Room temperature of 25 oC and relative humidity of 72 %. Thermal critical state level 2. Action: removal of operation equipment.

49,2°C

40 33,4°C 20 15,1°C

Figure 9. Thermogram carried out during field inspection.

Laboratory analyses:

• Tension (kV) 10 20 30 40 50 60 70

Measurement of leakage current and dielectric losses: Superior Section Leakage Current Dielectric (mA) Loss (W) 1.5 0.1168 6.2 0.4946 24.0 1.2179 32.1 2.4803 73.2 136 250.3

It was not possible to analyze the inferior section due to high losses.

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

Figure 10. Opening of the inferior unit.

Case 6:

13, 8 kV Surge Arrester. Substation: FTZ Description of occurrence: Inspection in 06/21/2005, at 19:20h. Room temperature of 26 oC and relative humidity of 72 %. Thermal critical state level 2. Action: removal of operation equipment. 41,8°C ase B*: 36,0°C

40

30

20 19,2°C

Figure 11. Thermogram carried out in the field during inspection.

Laboratory analyses:

• •

Measurement of leakage current and dielectric losses: It was not possible to carry out the analyses due to high losses. The equipment was submitted to a tension of 15 kV/ √3 in the laboratory and monitored with the IR Camera:

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

FLIR Systems

Ar1:max 67.3

76.9 °C

60

40

29.1

Figure 12. Thermal profile similar to that in the field.

Figure 13. Opening of the unit: 

Case 7:

13, 8 kV Surge Arrester. Substation: MTT Description of occurrence: Inspection in 08/06/2002, at 18:30h. Room temperature of 23 oC and relative humidity of 71 %. Thermal critical state level 2. Action: removal of operational equipment.

Fase C: 31,1°C

40,1°C 40

30

20 19,3°C

Figure 14. Thermograms carried out in the field during  inspection.

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

Laboratory analyses:

•

Measurement of lickage current and dielectrical l osses: they were not carried out.

Figure 15. Opening of the unit.

Case 8:

230 kV Surge Arrester. Substation: NTD Description of occurrence: Inspection in 02/16/2005, at 19:30h. Room temperature of 23 oC and relative humidity of 71 %. Action: external cleaning of porcelain and posterior inspection

38,1°C

38,1°C

30,1°C

30

25,3°C

20

20

18,4°C

18,4°C

Figure 16. Phase A

InfraMation 2006 Proceedings

30

Figure 16b. After cleaning 

ITC 115 A 2006-05-22

38,1°C

29,6°C

38,1°C

30

30

20

20

18,4°C

Figure 17. Phase B

18,4°C

Figure 17b. After cleaning 

38,1°C

FC: 31,1°C

38,1°C

25,3°C 30

30

20

20

18,4°C

Figure 18. Phase C

18,4°C

Figure 18b. After Cleaning 

SUMMARY To characterize heating “rings” in the body of the equipment it is necessary to do a study of the different phases from different angles; Whenever possible, the cleaning procedure of the porcelain and repetition of the measurement is recommended, as a way to reduce doubts regarding apparent heating due to pollution; The comparative evaluation proved to be more efficient, considering as premises the similar operational background, same maker and type; in all cases the cause is the loss of estanqueity with humidity penetration, increase of internal leakage current and heating. REFERENCE ITC – Infrared Training Center - Level II Course;

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22

InfraMation 2006 Proceedings

ITC 115 A 2006-05-22