**9. References**


source. A three-phase linear load with |*ZP*1| = 9.802 Ω and λ*P* = 0.81 (load model LM1) is also connected. The study shows that there is no harmonic problem in the system and that voltage distortion is below 0.05% [Table 7 in (Arendse & Atkinson-Hope, 2010)]. This can be analyzed from (22) because, considering that *rL* = 4.84/0.00079 = 6127 and *zP* = 9.802/0.00079 = 12408 (i.e., the three-phase linear load influence is negligible), the

In this chapter, the analytical study conducted in previous works on the parallel and series resonance in power systems with a Steinmetz circuit is unified and an expression unique to the location of both resonances is provided, which substantially improves those proposed in earlier works on the parallel resonance. This expression considers not only the impact of capacitor degradation on the resonance but also the resistance of the Steinmetz circuit

The sensitivity analysis reveals that the resonances mainly depend on the power system inductors and the single-phase load of the Steinmetz circuit. However, capacitor bank degradation and the R/X ratio of the Steinmetz circuit inductor can also strongly influence the resonance. Broadly speaking, Steinmtez circuit resonances with power system reactors appear at high-order harmonics. They only occur at low-order harmonics if the single-phase load impedance is small in comparison with the supply system reactance (i.e., in weak power systems) and the single-phase load power displacement factor is close to the unity value. The study also shows that the capacitor bank degradation and the resistance of the Steinmetz circuit inductor shift the resonance to higher harmonics. The analytical study results are validated with experimental measurements in a downscaled laboratory system and the study is applied to analyze several power systems with a Steinmetz circuit in the literature. Measurements in actual ac traction systems will be necessary to fully confirm

Future research should focus on the power system harmonic response "observed" from the railroad substation. The framework developed in the previous research and completed in this Chapter must make it possible to obtain analytical expressions to locate resonances from

ABB Power Transmission (n.d.). Multiple SVC installations for traction load balancing in

Arendse, C. & Atkinson-Hope, G. (2010). Design of a Steinmetz symmetrizer and application

Central Queensland. In: *Pamphlet A02-0134*, 26/02/2011, Available from

in unbalanced network. *Proceedings of the 45th International Universities Power* 

parallel resonance "observed" from the VSD is located at *kr*, a = 72.9.

inductor, which is another contribution to previous studies.

**7. Conclusion** 

these results.

the substation.

**9. References** 

**8. Acknowledgment** 

This work is supported by grant DPI2010-15448.

<http://www.abb.com/>.

*Engineering Conference (UPEC)*, pp. 1-6, 2010.


**8** 

*Iran* 

*Mefragh Company* 

**Stochastic Analysis of the Effect of Using** 

Switch mode electronic devices including Compact Fluorescent Lamp (CFL) and personal computers introduce capacitive power factor and current harmonics to the power system. Since middle 80's and with the expanding use of nonlinear switch mode electronic loads, concerns arose about their effect on the power systems. In many IEEE documents, it is recommended to study the effect of electronic loads. Switch mode devices have a capacitive power factor between 55 and 93 percent (Allexperts), which can cause the increase of reactive power and power loss. The power loss in an office building wirings due to the current harmonics may be more than twice that of the linear load equipment (Key et al., 1996). Capacity of the transformers may be reduced more than 50 per cent in the presence of

CFL is a more efficient and durable replacement of the traditional incandescent lamp. Replacing traditional light bulbs by CFLs has several advantages including energy saving, increase in the capacity of plants and distribution transformers, peak shaving, less carbon emission and customer costs. On average, 20 percent of the total use of electricity is consumed in lighting (Michalik et al., 1997), (Tavanir). However, the increase in the number of electronic devices especially the CFLs in power systems must be carefully planned. Replacing the incandescent light bulbs with CFLs means replacing the system's major Ohmic load with a capacitive load of high frequency harmonic components. In areas where lighting is a major use of electricity, e.g. places where natural gas or other fossil fuels are used for heating purposes, unplanned replacing of incandescent lamps with CFLs can introduce unexpected negative effects on the system. Also, in areas with a considerable number of other switch mode devices e.g. commercial areas with many office buildings it is important to plan the number of CFLs carefully. Most of the present studies on the effect of switch mode devices are based on tentative experiments and power factor measuring before and after using the devices in the power system (Gonos et al., 1999), and proposing a model

In order for studying such effects, it is better to classify the system equipment to the substation equipment and consumer side equipment. Dramatic changes in power quality indicators of the distribution systems may cause disorders or even damages in the consumer equipments. Such disorders are especially important for sensitive appliances such as

**1. Introduction** 

harmonic components (Schneider, 2009).

for the network has been less discovered.

medical and hospital devices.

**Harmonic Generators in Power Systems** 

Mohsen Abbas Pour Seyyedi and Amir Hossein Jahanikia

