ELECTRICAL PROBLEM
Thunder Strike
Thunder Strike
Thunder Strike
Thunder Strike
Grounding 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)
Grounding Resistance
Grounding Resistance 1. Length/depth of the ground electrode 2. Diameter of the ground electrode 3. Number of ground electrodes 4. Ground system design
Ground system design Single Ground Electrode
Ground system design Multiple Ground Electrode
Ground system design Mesh Network.
Ground system design Ground Plate
Tower Grounding
Measurement
Broken Insulation
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
Power Quality problem
Masalah yang dihasilkan harmonik Dua Faktor Daya *Total PF < DPF 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.
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
Motor dan Generator - Peningkatan pemanasan akibat rugi-rugi inti dan tembaga pada frekuensi harmonik - Berdenyut dan mengurangi torsi (penolakan starting atau peningkatan slip)
Pemanasan Transformer Tranformer memberikan rata-rata tegangan dan arus penuh (hanya) dengan sinusoidal, tegangan seimbang dan arus THD kurang dari 5 %
Derate Transformers Kapasitas rata-rata Transformer 100 kva Panas sama Kapasitas rata-rata Transformer 100 kva Phase C Current Beban Linear 100 kva Beban Harmonik 75 kva
Derating Transformers Faktor rugi-rugi arus Eddy (P ECR ) Contoh 1000 kva Dry Transformer Derating Dry Transformers Percent Loss % 1000 kva 3-8 1500 kva, 5kV HV 12-20 1500 kva, 15kV HV 9-15 Slide sebelumnya menunjukan K faktor = 7.6, dari tabel P ECR = 8% (.08) 1 + P ECR 1 + K * P ECR = % Kapasitas Oil Filled Transformers Percent Loss % 2500 kva, 480V,LV 1 > 1500 kva 5000 kva 1-5 > 5000 kva, kva 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
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
STANDAR
26 IEEE Defined Harmonic Current Limits
Standar dan Peraturan Harmonik I sc Harmonic Current Distortion Limits (Ih) in % of IL V 69 n kv / I h 11 11 h 17 17 h 23 23 h 35 35 h TDD L <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 TDD I 2 h h 2 I L 100% I h = magnitude of individual harmonic components (rms amps) h = harmonic order I L = maximum demand load current (rms amps) defined above