The Effect of Harmonics Caused by Non-Linear Loads and Power Imbalance Between Phases on Neutral Current

Öz

The operation of devices with different load types is related to the occurrence of distortions such as high current and voltage harmonics, phase and power imbalance. Electrical equipment may not operate correctly due to higher harmonics and power and phase imbalance. Neutral current is the result of harmonics and power and phase imbalance. In three-phase systems, current may flow in the neutral conductor due to the imbalance problem caused by the loads or the wrong wiring. Non-linear loads inject harmonic currents into the grid or source. When triple harmonics are present in the network, the neutral current is not zero even if the load is perfectly balanced. This can increase the risk of fire due to overheating of the neutral conductor due to overload. In this study, power parameters were measured by performing five measurements in three phases (Phase A, Phase B and Phase C) in three different facilities. The effects of load unbalance and triple harmonic values on neutral current are compared. Although the power imbalance standard error value in the first and second measurement was close to each other, there was approximately 30% variation between the triple harmonic values, while the difference in neutral current was 13.27 A. For the test system in the current study, it was concluded that triplen harmonics have more effect on the current in the neutral conductor than unbalanced loading.

Anahtar Kelimeler

• Power unbalance
• non-linear loads
• harmonic distortion
• power quality
• neutral current

Lineer Olmayan Yüklerin Sebep Olduğu Harmoniklerin ve Fazlar Arası Güç Dengesizliğinin Nötr Akımına Etkisi

Öz

Farklı yük çeşitlerine sahip cihazların çalışması, yüksek akım ve gerilim harmonikleri, faz ve güç dengesizliği gibi bozulmaların meydana gelmesiyle ilgilidir. Daha yüksek harmonikler ile güç ve faz dengesizliği nedeniyle elektrik ekipmanları doğru çalışmayabilir. Nötr akım, harmonik ile güç ve faz dengesizliği sonuçlarındandır. Üç fazlı sistemlerde yüklerin neden olduğu dengesizlik sorunundan veya kablo bağlantısında yapılan yanlışlıklardan kaynaklı olarak nötr iletkende akım akışı olabilir. Lineer olmayan yükler şebekeye veya kaynağa harmonik akımlar enjekte eder. Şebekede üçlü harmonikler mevcut olduğunda, yük mükemmel bir şekilde dengelenmiş olsa bile nötr akım sıfır değildir. Bu da nötr iletkeninin aşırı yüklenmesine bağlı olarak ısınması nedeniyle yangın riskini artırabilir. Bu çalışmada üç farklı tesiste beş ölçüm, üç fazda (Faz A, Faz B ve Faz C) yapılarak güç parametreleri ölçülmüştür. Yük dengesizliği ile üçlü harmonik değerlerinin nötr akımına etkisi karşılaştırılmıştır. Birinci ve ikinci ölçümdeki güç dengesizliği standart hata değeri birbirine yakın olmasına karşın üçlü harmonik değerler arasında yaklaşık %30’luk değişkenlik var iken nötr akımda oluşan fark 13.27 A olmuştur. Çalışmadaki test edilen sistem için triplen harmoniklerin, dengesiz yüklenmeye göre nötr iletkende oluşan akım üzerinde daha fazla etkisinin olduğu sonucuna varılmıştır.

Anahtar Kelimeler

• Güç dengesizliği
• lineer olmayan yükler
• harmonik bozulma
• güç kalitesi
• nötr akım

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