# Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{iz}) has infinite value. It is also considered that the Petersen coil is ideal, i.e., in the equivalent scheme of the coil only its reactance occurs, and that the electrical resistance (R

_{PC}) equivalent to the coil has the value zero. The paper shows that accepting these simplifications using the mathematical model to calculate the single-phase fault current can lead to unacceptable errors. Very large errors can be made even if the R

_{iz}and R

_{PC}parameters are not neglected in the mathematical model, but the values considered for them are far from reality. As a result, the phase angle between the current through the Petersen coil (${i}_{PC}$) and its voltage (${u}_{PC}$) is less than 90°. The phase difference between the voltage ${u}_{PC}$ and the current ${i}_{PC}$ is denoted by ${\phi}_{PC}$. Thus, in the equivalent scheme the coil also intervenes in the electrical resistance, and not only the inductive reactance. Furthermore, the capacitive current of the medium voltage network (${i}_{c}$) has an active component, which causes an electrical resistance to intervene in the equivalent scheme in parallel with the capacitive reactance. The phase difference between the zero-sequence voltage of the medium voltage bus bars in the transformer substation (${u}^{0}$) and the total capacitive current of electrical networks must be less than 90°. The phase difference between the zero-sequence voltage of the medium voltage bus bars in the transformer substation (${u}^{0}$) and the total capacitive current of electrical networks is denoted by ${\phi}_{c}$. In the paper, it is considered that these phase angles vary in the range [83°–90°]. This paper also analyzes the influence of the resistance at the fault location R

_{t}on the single-phase fault current. For this parameter, the values 8 Ω, 100 Ω, 268 Ω, 575 Ω and 1100 Ω were considered.

- T1 and T2 power transformers with apparent powers 10 MVA and 16 MVA, respectively, and voltages of 110/20 kV. Transformer T1 is not connected to bus bar 1 (this results from Figure 1), so it does not influence the fault;
- NUT utility transformer of 20/0.4 kV having the connection of the primary winding in a zig-zag, and which is used to achieve the artificial neutral. The nominal apparent power is 1200/250 kVA (NUT has different apparent powers for the primary and secondary winding, because the 20 kV winding of the transformer is also used to create the null point of the 20 kV grid, to which the Petersen coil is connected, and the apparent power of the primary winding is higher than of the secondary winding. This solution is used in most 110/20 kV substations in Romania.);
- UT—utility transformer, at 20/0.4 kV with an apparent power of 250 kVA;
- L1—the 20 kV line on which the single-phase fault occurs, having practically zero capacitive current, with the fault being caused in the line cell, and the line separator open;
- L2—the 20 kV line whose capacitive current is 6.9 A and is out of phase before the zero-sequence voltage by 75° (1.31 radians);
- L3—the 20 kV line whose capacitive current is 20.5 A and is out of phase before the zero-sequence voltage by 88° (1.54 radians);
- L4—the 20 kV line whose capacitive current is 21.1 A, and is out of phase before the zero-sequence voltage by 86° (1.5 radians);
- R
_{t}—the resistance at the fault location; - BCS—the bus coupler switch;
- MG1—the measuring group of bus bar system 1;
- MG2—the measuring group of bus bar system 2.

## 2. The Mathematical Model for the Analysis of a Single-Phase-to-Ground Fault

_{1}, U

_{2}and U

_{3}are the phase voltages represented in the complex, ${\underset{\_}{I}}_{1},{\underset{\_}{I}}_{2}\mathrm{and}{\underset{\_}{I}}_{3}$ are the phase currents represented in the complex, and ${\underset{\_}{Z}}_{1},{\underset{\_}{Z}}_{2}\mathrm{and}{\underset{\_}{Z}}_{3}$ are the phase impedances represented in the complex. The sequence voltages as a function of the phase voltages are expressed by the relations [23,24,25],

## 3. Computing of Single-Phase-to-Ground Fault Current

_{1}(point K in Figure 1). The sequence schemes corresponding to this defect are shown in Figure 4.

- ${\underset{\_}{U}}_{ph}$—the electromotive forces of Thévenin equivalent generators, of the plus sequence and of the network of 20 kV as seen from the place of fault (the phase voltage of the faulty phase before causing the fault);
- ${\underset{\_}{Z}}_{T2}^{+}$—the plus-sequence impedance of the transformer T2 in Figure 1;
- ${\underset{\_}{Z}}_{T2}^{-}$—the minus-sequence impedance of the transformer T2 in Figure 1;
- ${\underset{\_}{Z}}_{L1}^{+}$—the plus-sequence impedance from the substation bars to the fault location of the fault line (L1 in Figure 1);
- ${\underset{\_}{Z}}_{L1}^{-}$—the minus-sequence impedance from the substation bars to the fault location of the fault line (L1 in Figure 1);
- ${\underset{\_}{Z}}_{L1}^{0}$—the zero-sequence impedance from the substation bars to the fault location of the fault line (L1 in Figure 1);
- ${\underset{\_}{Z}}_{NUT}^{+}$—the plus-sequence impedance of the own service transformer used to achieve the artificial neutral of the 20 kV network (transformer NUT in Figure 1);
- ${\underset{\_}{Z}}_{NUT}^{-}$—the minus-sequence impedance of the own service transformer used to achieve the artificial neutral of the 20 kV network (transformer NUT in Figure 1);
- ${\underset{\_}{Z}}_{NUT}^{0}$—the zero-sequence impedance of the own service transformer used to achieve the artificial neutral of the 20 kV network (transformer NUT in Figure 1);
- ${\underset{\_}{Z}}_{PC}$—the impedance of the Petersen coil;
- ${X}_{c}^{0}$—the zero-sequence capacitive reactance of the electrical network with voltage 20 kV;
- ${R}_{in}$—the equivalent electrical resistance corresponding to active power losses in the insulation of the electrical network with a voltage of 20 kV;
- ${R}_{t}$—the resistance at the fault location.

_{fc}) place is computing with the relation,

_{c}.

## 4. Experimental Results

- ${i}_{1}^{0}$—the zero-sequence current (fault current) of the line L
_{1}on which the fault occurred; - ${i}_{2}^{0},{i}_{3}^{0},{i}_{4}^{0},$—the zero-sequence currents of the non-fault lines;
- ${i}_{PC}$—the current through the Petersen coil;
- ${u}_{1},{u}_{2},{u}_{3}$—the phase voltages of the medium voltage bars in the transformer substation;
- ${u}^{0}$—the zero-sequence voltage of the medium voltage bars in the transformer substation;
- ${u}_{PC}$—the Petersen coil voltage.

_{t}= 8 Ω, and Figure 7 shows the oscillogram obtained for R

_{t}= 1100 Ω.

_{t}= 1100 Ω, the transient component, both in the current line with fault and in the currents of the lines without defect, was much smaller. For this reason the waveforms of currents were practically sinusoidal. The voltage waveform, both in the oscillogram from Figure 6 when R

_{t}= 8 Ω, as well as in the oscillogram in Figure 7 when R

_{t}= 1100 Ω, was sinusoidal, a hypothesis that was accepted in the analytical calculation of the fault current. The values of currents and voltages during the single-phase-to-ground fault obtained from the measurements in the real network of 20 kV are presented in Table 11.

## 5. Discussion

_{fe}) and those obtained by analytical calculation (I

_{fc}). The difference in the percentages of the effective values of the fault current obtained experimentally and analytically was calculated with the relation,

^{0}and current i

_{c}was 85.3$\xb0$, when the insulation of the 20 kV network was ideal (phase shift between u

^{0}and i

_{c}is 90$\xb0$). The phase differences between the voltage ${u}_{PC}$ and the $i{u}_{PC}$ current were 83°, 84°, 85°, 86°, 87°, 88°, 89° and 90°, and the values of the resistance at the fault location were 8 Ω, 100 Ω, 268 Ω, 575 Ω and 1100 Ω. The results obtained are presented in Table 12 and Table 13, respectively.

_{t}= 8 Ω and the minimum value of error was 24.3% if R

_{t}= 1100 Ω.

## 6. Conclusions

_{iz}and R

_{PC}do not correspond to reality. In order to reduce these differences, it is necessary to know the more precise values of the mentioned parameters.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 5.**Wiring diagram of the data acquisition equipment and recording of the measured parameters.

**Figure 6.**The waveform of currents and voltages during the single-phase fault when R

_{t}= 8 Ω and the network operates in resonance regime.

**Figure 7.**The waveform of currents and voltages during the single-phase fault when R

_{t}= 1100 Ω and the network operates in resonance regime.

**Figure 8.**The dependence of difference between the effective values of the fault current, determined experimentally and analytically, and function on the difference phase between ${u}_{PC}$ and ${i}_{PC}$, when ${\phi}_{c}=85.3\xb0$.

**Figure 9.**The dependence of difference between the effective values of the fault current, determined experimentally and analytically, and function on the difference phase between ${u}_{PC}$ and ${i}_{PC}$, when ${\phi}_{c}=90\xb0$.

**Table 1.**The values of the sequence impedances of the elements in the scheme shown in Figure 1.

Name of Electrical Equipment | ${\underset{\_}{\mathit{Z}}}^{+}$ [Ω] | ${\underset{\_}{\mathit{Z}}}^{-}$ [Ω] | ${\underset{\_}{\mathit{Z}}}^{0}$ [Ω] |
---|---|---|---|

T2 (Y_{0}/∆) | 0.18 + j3.1 | 0.18 + j3.1 | $\infty $ |

NPT(Z_{0}/Y_{0}) | 2.91 + j752 | 2.91 + j752 | 2.78 + j8.34 |

20 kV lines [Ω/km] | 0.52 + j0.9 | 0.52 + j0.9 | 0.57 + j2.7 |

Petersen coil | j254.9 | j254.9 | j764.7 |

20 kV Line | ${\mathit{\phi}}_{\mathit{c}}^{\prime}\phantom{\rule{0ex}{0ex}}[\xb0]$ | Capacitive Current | (R_{iz})[Ω] | X_{c}^{0}[Ω] | |
---|---|---|---|---|---|

Active [A] | Reactive [A] | ||||

L2 | 75° | 1.79 | 6.66 | 20,997 | 5643 |

L3 | 88° | 0.72 | 20.5 | 52,202 | 1833 |

L4 | 86° | 1.47 | 21.05 | 25,568 | 1786 |

Total | 85.3° | 3.98 | 48.21 | 9444 | 779.6 |

Order Number | ${\mathit{\phi}}_{\mathit{c}}$ [°] | Capacitive Current | R_{iz}[Ω] | X_{c}^{0}[Ω] | |
---|---|---|---|---|---|

Active [A] | Reactive [A] | ||||

1 | 86° | 3.37 | 48.26 | 11,153 | 778.8 |

2 | 87° | 2.53 | 48.31 | 14,857 | 778.1 |

3 | 88° | 1.67 | 48.34 | 22,507 | 777.6 |

4 | 89° | 0.84 | 48.36 | 44,747 | 777.2 |

5 | 90° | 0 | 48.37 | $\infty $ | 777.1 |

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}[\xb0]$ | ${\mathit{R}}_{\mathit{P}\mathit{C}}\left[\mathsf{\Omega}\right]$ | ${\mathit{X}}_{\mathit{P}\mathit{C}}\left[\mathsf{\Omega}\right]$ |
---|---|---|---|

1 | 90$\xb0$ | 0 | 276.6 |

2 | 89$\xb0$ | 4.83 | 276.5 |

3 | 88$\xb0$ | 9.65 | 276.4 |

4 | 87$\xb0$ | 14.48 | 276.2 |

5 | 86$\xb0$ | 19.29 | 275.9 |

6 | 85$\xb0$ | 24.1 | 275.5 |

7 | 84$\xb0$ | 28.91 | 275.1 |

8 | 83$\xb0$ | 33.71 | 274.5 |

**Table 5.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 85.3° (experimentally determined angle value ${\phi}_{c}$ in the real network 20 kV).

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 5.32 | 4.95 | 4.93 | 4.48 | 3.86 |

2 | 89$\xb0$ | 5.94 | 5.50 | 5.43 | 4.87 | 4.12 |

3 | 88$\xb0$ | 6.61 | 6.08 | 5.96 | 5.27 | 4.38 |

4 | 87$\xb0$ | 7.31 | 6.69 | 6.49 | 5.67 | 4.64 |

5 | 86$\xb0$ | 8.03 | 7.39 | 7.04 | 6.07 | 4.89 |

6 | 85$\xb0$ | 8.77 | 7.94 | 7.58 | 6.46 | 5.13 |

7 | 84$\xb0$ | 9.52 | 8.57 | 8.11 | 6.76 | 5.36 |

8 | 83° | 10.27 | 9.20 | 8.64 | 7.21 | 5.58 |

**Table 6.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 86$\xb0$.

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 4.86 | 4.82 | 4.60 | 4.23 | 3.69 |

2 | 89$\xb0$ | 5.46 | 5.36 | 5.07 | 4.60 | 3.93 |

3 | 88$\xb0$ | 6.11 | 5.95 | 5.57 | 4.98 | 4.19 |

4 | 87$\xb0$ | 6.79 | 6.56 | 6.09 | 5.37 | 4.45 |

5 | 86$\xb0$ | 7.50 | 7.19 | 6.62 | 5.76 | 4.70 |

6 | 85$\xb0$ | 8.23 | 7.83 | 7.15 | 6.15 | 4.94 |

7 | 84$\xb0$ | 8.97 | 8.48 | 7.68 | 6.53 | 5.17 |

8 | 83° | 9.73 | 9.13 | 8.20 | 6.89 | 5.39 |

**Table 7.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 87$\xb0$.

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 4.30 | 4.32 | 4.17 | 3.90 | 3.47 |

2 | 89$\xb0$ | 4.83 | 4.81 | 4.59 | 4.22 | 3.69 |

3 | 88$\xb0$ | 5.43 | 5.35 | 5.07 | 4.60 | 3.94 |

4 | 87$\xb0$ | 6.09 | 5.94 | 5.57 | 4.98 | 4.20 |

5 | 86$\xb0$ | 6.77 | 6.56 | 6.09 | 5.38 | 4.46 |

6 | 85$\xb0$ | 7.49 | 7.19 | 6.62 | 5.77 | 4.71 |

7 | 84$\xb0$ | 8.22 | 7.83 | 7.15 | 6.16 | 4.95 |

8 | 83° | 8.96 | 8.48 | 7.68 | 6.53 | 5.18 |

**Table 8.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 88$\xb0$.

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 3.97 | 3.92 | 3.82 | 3.63 | 3.31 |

2 | 89$\xb0$ | 4.39 | 4.30 | 4.15 | 3.89 | 3.47 |

3 | 88$\xb0$ | 4.91 | 4.79 | 4.56 | 4.22 | 3.69 |

4 | 87$\xb0$ | 5.50 | 5.34 | 5.06 | 4.59 | 3.94 |

5 | 86$\xb0$ | 6.14 | 5.92 | 5.56 | 4.98 | 4.20 |

6 | 85$\xb0$ | 6.81 | 6.54 | 6.08 | 5.37 | 4.46 |

7 | 84$\xb0$ | 7.51 | 7.17 | 6.61 | 5.77 | 4.71 |

8 | 83° | 8.23 | 7.71 | 7.14 | 6.15 | 4.95 |

**Table 9.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 89$\xb0$.

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 3.67 | 3.66 | 3.60 | 3.49 | 3.26 |

2 | 89$\xb0$ | 3.97 | 3.92 | 3.82 | 3.64 | 3.32 |

3 | 88$\xb0$ | 4.40 | 4.32 | 4.17 | 3.90 | 3.49 |

4 | 87$\xb0$ | 4.92 | 4.80 | 4.59 | 4.24 | 3.71 |

5 | 86$\xb0$ | 5.51 | 5.35 | 5.07 | 4.61 | 3.96 |

6 | 85$\xb0$ | 6.15 | 5.93 | 5.57 | 4.99 | 4.21 |

7 | 84$\xb0$ | 6.82 | 6.55 | 6.10 | 5.39 | 4.47 |

8 | 83° | 7.52 | 7.18 | 6.62 | 5.78 | 4.72 |

**Table 10.**Effective value of the fault current depending on ${\phi}_{PC}$, when ${\phi}_{c}$ = 90$\xb0$.

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | I_{fc} [A] | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 3.37 | 3.23 | 3.39 | 3.34 | 3.23 |

2 | 89$\xb0$ | 3.51 | 3.34 | 3.47 | 3.36 | 3.16 |

3 | 88$\xb0$ | 3.83 | 3.62 | 3.72 | 3.55 | 3.25 |

4 | 87$\xb0$ | 4.28 | 4.03 | 4.10 | 3.85 | 3.45 |

5 | 86$\xb0$ | 4.83 | 4.53 | 4.56 | 4.21 | 3.70 |

6 | 85$\xb0$ | 5.46 | 5.08 | 5.07 | 4.62 | 3.97 |

7 | 84$\xb0$ | 6.12 | 5.67 | 5.61 | 5.03 | 4.25 |

8 | 83° | 6.82 | 6.29 | 6.17 | 5.46 | 4.53 |

R_{t} [Ω] | ${\mathit{I}}_{1}^{0}={\mathit{I}}_{\mathit{f}\mathit{e}}$ [A] | ${\mathit{I}}_{2}^{0}$ [A] | ${\mathit{I}}_{3}^{0}\left[\mathbf{A}\right]$ | ${\mathit{I}}_{4}^{0}\left[\mathbf{A}\right]$ | ${\mathit{I}}_{\mathit{P}\mathit{C}}\left[\mathbf{A}\right]$ | ${\mathit{U}}_{1}\left[\mathbf{V}\right]$ | ${\mathit{U}}_{2}\left[\mathbf{V}\right]$ | ${\mathit{U}}_{3}\left[\mathbf{V}\right]$ | ${\mathit{U}}^{0}\left[\mathbf{V}\right]$ | ${\mathit{U}}_{\mathit{P}\mathit{C}}\left[\mathbf{V}\right]$ |
---|---|---|---|---|---|---|---|---|---|---|

8 | 7.8 | 7.0 | 20.5 | 21.1 | 45.3 | 63 | 21,700 | 21,700 | 12,619 | 12,530 |

100 | 7.2 | 6.9 | 20.3 | 20.9 | 44.9 | 725 | 21,800 | 21,300 | 12,507 | 12,419 |

268 | 6.9 | 6.5 | 19.1 | 19.7 | 42.2 | 1850 | 21,900 | 21,900 | 11,758 | 11,675 |

575 | 6.1 | 6.3 | 18.4 | 18.9 | 40.7 | 3520 | 21,900 | 19,500 | 11,338 | 11,258 |

1100 | 5.1 | 5.6 | 16.3 | 18.6 | 36.3 | 5610 | 15,500 | 21,700 | 10,112 | 10,041 |

**Table 12.**The difference between the effective values of the fault current determined experimentally and analytically (φ

_{c}= 85.3°).

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | Ɛ% | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 31.8 | 31.3 | 28.6 | 26.6 | 24.3 |

2 | 89$\xb0$ | 23.8 | 23.6 | 21.3 | 20.2 | 19.2 |

3 | 88$\xb0$ | 15.3 | 15.6 | 13.6 | 13.6 | 14.1 |

4 | 87$\xb0$ | 6.3 | 4.17 | 5.94 | 7.05 | 9.02 |

5 | 86$\xb0$ | −2.95 | −2.64 | −2.02 | 0.50 | 4.12 |

6 | 85$\xb0$ | −12.4 | −10.3 | −9.86 | −5.90 | −0.59 |

7 | 84$\xb0$ | −22.1 | −19.0 | −17.5 | −10.8 | −5.10 |

8 | 83° | −31.7 | −27.8 | −25.2 | −18.2 | −9.41 |

**Table 13.**The difference between the effective values of the fault current determined experimentally and analytically (φ

_{c}= 90°).

Order Number | ${\mathit{\phi}}_{\mathit{P}\mathit{C}}\phantom{\rule{0ex}{0ex}}[\xb0]$ | Ɛ% | ||||
---|---|---|---|---|---|---|

R_{t} = 8 Ω | R_{t} = 100 Ω | R_{t} = 268 Ω | R_{t} = 575 Ω | R_{t} = 1100 Ω | ||

1 | 90$\xb0$ | 56.8 | 55.1 | 50.9 | 45.2 | 36.7 |

2 | 89$\xb0$ | 55.0 | 53.6 | 49.7 | 44.9 | 38.0 |

3 | 88$\xb0$ | 50.9 | 49.7 | 46.1 | 41.8 | 36.3 |

4 | 87$\xb0$ | 45.1 | 44.0 | 40.6 | 36.9 | 32.4 |

5 | 86$\xb0$ | 38.1 | 37.1 | 33.9 | 31.0 | 27.5 |

6 | 85$\xb0$ | 30.0 | 29.4 | 26.5 | 24.3 | 22.2 |

7 | 84$\xb0$ | 21.5 | 21.3 | 18.7 | 17.5 | 16.7 |

8 | 83° | 12.6 | 12.6 | 10.6 | 10.5 | 11.2 |

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## Share and Cite

**MDPI and ACS Style**

Toader, D.; Greconici, M.; Vesa, D.; Vintan, M.; Solea, C.
Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current. *Energies* **2021**, *14*, 1330.
https://doi.org/10.3390/en14051330

**AMA Style**

Toader D, Greconici M, Vesa D, Vintan M, Solea C.
Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current. *Energies*. 2021; 14(5):1330.
https://doi.org/10.3390/en14051330

**Chicago/Turabian Style**

Toader, Dumitru, Marian Greconici, Daniela Vesa, Maria Vintan, and Claudiu Solea.
2021. "Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current" *Energies* 14, no. 5: 1330.
https://doi.org/10.3390/en14051330