ELECTRICAL PROBLEM Page 1

ELECTRICAL PROBLEM

Thunder Strike

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Thunder Strike

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Thunder Strike

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Thunder Strike

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Grounding 

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Ideally the ground resistance of a system is zero ohms NFPA & IEEE: Recommends a ground resistance value of 5 Ohm or less. Telecommunications Industry: Often uses 5.0 ohms or less as their value for grounding or bonding NEC: Make sure the system to ground is 25.0 ohms or less. In facilities with sensitive equipment, it should be 5.0 ohms or less. (source – NEC 250.56)

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Grounding Resistance

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Grounding Resistance 

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1. Length/depth of the ground electrode 2. Diameter of the ground electrode 3. Number of ground electrodes 4 . Ground system design

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Ground system design

Single Ground Electrode

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Ground system design

Multiple Ground Electrode

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Ground system design

Mesh Network.

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Ground system design

Ground Plate

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Tower Grounding

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Measurement

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Broken Insulation

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Insulation There are a number of industry standards that give guidelines for insulation testing in the field: • NETA MTS-2001 Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems • IEEE 43-2000 Recommended Practice for Testing Insulation Resistance of Rotating Machinery • IEC 60034-18 Rotating electrical machines - Part 18: Functional evaluation of insulation systems • IEC 61557-2 Electrical Safety in Low Voltage Distribution Systems up to 1000 V ac and 1500 V dc

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Power Quality problem 

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Masalah yang dihasilkan harmonik Dua Faktor Daya

*Total PF < DPF

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Perpindahan / Displacement Power Faktor  Sama

dengan perpindahan sudut antara fundamental tegangan dan fundamental arus  Sama dengan kW / kVA hanya untuk sinusoidal V, I 

Total Power Faktor  Ukuran

dari kW / kVA  Termasuk efek harmonik  Kapasitor yang benar hanya perpindahan PF.

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Total harmonik Distorsi 0%

33%

39%

44%

Peak

100%

133%

168%

204%

RMS

100%

105%

108%

110%

3. Tersandung gangguan di pemutus sirkuit Meningkatkan Termal RMS Meningkatkan Magnitude Puncak 4. Sekering putus

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Motor dan Generator - Peningkatan pemanasan akibat rugi-rugi inti dan tembaga pada frekuensi harmonik - Berdenyut dan mengurangi torsi (penolakan starting atau peningkatan slip)

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Pemanasan Transformer 

Tranformer memberikan rata-rata tegangan dan arus penuh (hanya) dengan sinusoidal, tegangan seimbang dan arus THD kurang dari 5%

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Derate Transformers

Kapasitas rata-rata Transformer 100 kVA

Phase C Current

Beban Linear 100 kVA

Panas sama Beban Harmonik 75 kVA Kapasitas rata-rata Transformer 100 kVA

Derating Transformers

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Faktor rugi-rugi arus Eddy (PECR)

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Contoh 1000 kVA Dry Transformer Derating

Dry Transformers  1000 kVA  1500 kVA, 5kV HV  1500 kVA, 15kV HV

Oil Filled Transformers  2500 kVA, 480V,LV > 1500 kVA  5000 kVA > 5000 kVA, kVA

Percent Loss % 3-8 12-20 9-15

Slide sebelumnya menunjukan K faktor = 7.6, dari tabel PECR= 8% (.08)

1 + PECR

1 + K * PECR= % Kapasitas Percent Loss % 1 1-5 9-15

** in table above, always assume the worse case use the maximum values

% Kapasitas = 80 % (.80) kVA lama* % Kapasitas = kVA baru

1000kVA * .80 = 800 kVA www.tridinamika.com

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Masalah Kapasitor

◦ Penurunan impedansi dengan frekuensi ◦ Masalah resonansi

Masalah Kapasitor Karena impedansi yang lebih rendah, kapasitor bahkan lebih rentan terhadap tatanan harmonik yang lebih tinggi. Jika tida diproteksi dari stres harmonik, suatu kapasitor bisa segera gagal www.tridinamika.com

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STANDAR

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IEEE Defined Harmonic Current Limits

26

Standar dan Peraturan Harmonik Harmonic Current Distortion Limits (Ih) in % of IL V n  69 kV

I sc / I L

h  11

11  h  17 17  h  23 23  h  35

35  h

TDD

<20

4.0

2.0

1.5

0.6

0.3

5.0

20-50

7.0

3.5

2.5

1.0

0.5

8.0

50-100

10.0

4.5

4.0

1.5

0.7

12.0

100-1000

12.0

5.5

5.0

2.0

1.0

15.0

>1000

15.0

7.0

6.0

2.5

1.4

20.0

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I TDD 

h2

IL

2 h

 100%

Ih = magnitude of individual harmonic components (rms amps) h = harmonic order IL = maximum demand load current (rms amps) defined above