Diagnosis of medium voltage XLPE cables by high voltage dielectric spectroscopy

2002 ◽  
Author(s):  
P. Werelius ◽  
B. Holmgren ◽  
U. Gafvert
Keyword(s):  
High Voltage ◽  
Dielectric Spectroscopy ◽  
Medium Voltage

New electrical stimulation technologies for sheep carcasses New electrical stimulation technologies for sheep carcasses

2005 ◽  
Vol 45 (5) ◽  
pp. 575 ◽  
Author(s):  
F. D. Shaw ◽  
S. R. Baud ◽  
I. Richards ◽  
D. W. Pethick ◽  
P. J. Walker ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
High Voltage ◽  
Consumer Satisfaction ◽  
Electrode System ◽  
Constant Current ◽  
Eating Quality ◽  
Meat Eating ◽  
Medium Voltage ◽  
Sheep Meat ◽  
Maximum Voltage

High voltage electrical stimulation applied to the lamb carcass at the end of the dressing procedure often leads to an improvement in overall product quality by reducing the incidence of toughness. It would be advantageous if the same results could be consistently achieved with the use of lower, safer, voltages — medium voltage electrical stimulation. Experiments were conducted to determine the effect of medium voltage electrical stimulation applied to wool-on carcasses on meat quality as assessed using the Sheep Meat Eating Quality protocols. A further experiment examined the interaction of electrical stimulation and meat aging time on the consumer acceptance of lamb meat. In the first experiment, 3 treatments: control (non-stimulated), medium voltage electrical stimulation (applied to the wool-on carcass) and high voltage electrical stimulation (applied at the completion of dressing) were examined. Samples of the loin (LTL) and rump (GM) muscles were evaluated by consumers using Sheep Meat Eating Quality protocols. For both muscles, the consumers gave higher scores for tenderness, juiciness, flavour and overall acceptability to the stimulated product (P<0.001). There were no statistically significant differences between the 2 stimulation treatments. The second experiment was conducted at a commercial lamb-processing abattoir that had installed a prototype automated electrode system designed to work at chain speed. Lambs received either no stimulation (control), low current medium voltage electrical stimulation (constant current 300 mA peak, 15 Hz, maximum voltage 550 V peak) or high current medium voltage electrical stimulation (constant current 600 mA peak, 15 Hz, maximum voltage 550 V peak) immediately after sticking. Electrical stimulation improved both the objective and sensory (Sheep Meat Eating Quality) eating quality attributes of lamb loin muscle when assessed following 2 days of ageing. When expressed according to consumer satisfaction rating, 30, 37 and 70% of the loins receiving low, high or no electrical stimulation, respectively, were rated as unsatisfactory at 2 days of ageing. At 4 days of ageing no loins from carcasses in the low stimulation treatment were rated by consumers to be unsatisfactory (P<0.05) compared with either non-stimulated (40%) or high-stimulated loins (35%). With respect to the effects of aging meat, electrical stimulation improved the consumer score at 2 days post-stunning by 8.9 and 4.7 points for tenderness and overall liking, respectively. Further linear improvements due to aging were similar for both electrical stimulation and unstimulated products. Under conditions of no electrical stimulation used in this experiment, 10 days aging results in tenderness and overall liking scores greater than 60 and with ES similar scores are achieved in 5 days. Consumer scores over 60 greatly reduce the chance of meat being classified as unsatisfactory.

scholarly journals Operation Modes of HV/MV Substations

2009 ◽  
Vol 25 (25) ◽  
pp. 81-86
Author(s):  
Josifs Survilo ◽  
Antons Kutjuns
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Warm Season ◽  
Electrical Energy ◽  
Cold Season ◽  
Power Losses ◽  
Medium Voltage ◽  
The Third ◽  
Operation Modes ◽  
Mode 3

Operation Modes of HV/MV SubstationsA distribution network consists of high voltage grid, medium voltage grid, and low voltage grid. Medium voltage grid is connected to high voltage grid via substations with HV/MV transformers. The substation may contain one, mostly two but sometimes even more transformers. Out of reliability and expenditure considerations the two transformer option prevail over others mentioned. For two transformer substation, there may be made choice out of several operation modes: 1) two (small) transformers, with rated power each over 0.7 of maximum substation load, permanently in operation; 2) one (big) transformer, with rated power over maximum substation load, permanently in operation and small transformer in constant cold reserve; 3) big transformer in operation in cold season, small transformer-in warm one. Considering transformer load losses and no load losses and observing transformer loading factor β it can be said that the mode 1) is less advantageous. The least power losses has the mode 3). There may be singled out yet three extra modes of two transformer substations: 4) two big transformers in permanent operation; 5) one big transformer permanently in operation and one such transformer in cold reserve; 6) two small transformers in operation in cold season of the year, in warm season-one small transformer on duty. At present mostly two transformers of equal power each are installed on substations and in operation is one of them, hence extra mode 5). When one transformer becomes faulty, it can be changed for smaller one and the third operation mode can be practiced. Extra mode 4) is unpractical in all aspects. The mode 6) has greater losses than the mode 3) and is not considered in detail. To prove the advantage of the third mode in sense of power losses, the notion of effective utilization time of power losses was introduced and it was proven that relative value of this quantity diminishes with loading factor β. The use of advantageous substation option would make it possible to save notable amount of electrical energy but smaller transformer lifetime of this option must be taken into account as well.

scholarly journals Novel Enhanced Modular Multilevel Converter for High-Voltage Direct Current Transmission Systems

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2257
Author(s):  
Dimitrios Vozikis ◽  
Fahad Alsokhiry ◽  
Grain Philip Adam ◽  
Yusuf Al-Turki
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Medium Voltage ◽  
High Voltage Direct Current ◽  
Current Transmission ◽  
The Cost ◽  
Voltage Harmonics ◽  
Chain Links

This paper proposes an enhanced modular multilevel converter as an alternative to the conventional half-bridge modular multilevel converter that employs a reduced number of medium-voltage cells, with the aim of improving waveforms quality in its AC and DC sides. Each enhanced modular multilevel converter arm consists of high-voltage and low-voltage chain-links. The enhanced modular multilevel converter uses the high-voltage chain-links based on medium-voltage half-bridge cells to synthesize the fundamental voltage using nearest level modulation. Although the low-voltage chain-links filter out the voltage harmonics from the voltage generated by the high-voltage chain-links, which are rough and stepped approximations of the fundamental voltage, the enhanced modular multilevel converter uses the nested multilevel concept to dramatically increase the number of voltage levels per phase compared to half-bridge modular multilevel converter. The aforementioned improvements are achieved at the cost of a small increase in semiconductor losses. Detailed simulations conducted in EMPT-RV and experimental results confirm the validity of the proposed converter.

scholarly journals Control of Diffuse Vacuum Arc Using Axial Magnetic Fields in Commercial High Voltage Switchgear

2019 ◽  
Vol 6 (1) ◽  
pp. 19-22
Author(s):  
S. Giere ◽  
T. Heinz ◽  
A. Lawall ◽  
C. Stiehler ◽  
E. D. Taylor ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
High Voltage ◽  
Short Circuit ◽  
Dielectric Behavior ◽  
Vacuum Arc ◽  
Minimal Amount ◽  
Stress Tests ◽  
Extensive Experience ◽  
Medium Voltage ◽  
Vacuum Interrupter

During the development of a commercial vacuum interrupter for application in HV (high voltage) switchgear at a rated voltage of 145kV, we investigated the behavior of vacuum arcs controlled by axial magnetic fields (AMF). AMF arc control is already extensively used in medium voltage (1-52kV) applications, the key difference is the 2-3 times larger contact gap and the corresponding reduction of the AMF strength for HV applications. We conducted several stress tests with short circuit currents up to 40kA, thus not only testing the interrupting capability, but also the electrical endurance of such a contact system. We also investigated the dielectric behavior of the vacuum interrupter by testing the capacitive switching duty. Overall, the contacts were used in about 40 operations at high currents. Despite this large number of operations, they showed a minimal amount of contact erosion and damage and demonstrated behavior very similar to the extensive experience with MV vacuum interrupters. In line with simulation results, we conclude that even at high contact gaps and currents, a diffuse vacuum arc was maintained which distributed the arc energy evenly over the contacts.

scholarly journals State Estimation and Determination of Flexibility Potential in Medium Voltage Networks*

2019 ◽  
Vol 217 ◽  
pp. 01013
Author(s):  
Florian Rewald ◽  
Oliver Pohl ◽  
Ulf Häger ◽  
Christian Rehtanz
Keyword(s):  
State Estimation ◽  
High Voltage ◽  
Management System ◽  
Congestion Management ◽  
System Operation ◽  
Research Project ◽  
Medium Voltage ◽  
Real Medium ◽  
High Voltage System

This paper describes how flexibility of medium voltage systems can be used for operation of high voltage systems. This is explained using the example of a congestion management system for high voltage networks developed in the research project IDEAL. First, it is explained to what extent flexibility is required for high voltage system operation. After that, the entire congestion management system with flexibility of medium voltage systems is presented. Then, methodology for observability analysis, state estimation and determination of flexibility potential is shown. Finally, the implementation of the methodology in two real medium voltage systems is described.

Dielectric Spectroscopy of Polyimide Films Treated by Nanosecond High Voltage Pulsed Driven Electrical Discharges in Water

2015 ◽  
Vol 13 (2) ◽  
pp. 253-257 ◽  
Author(s):  
Camelia Miron ◽  
Jie Zhuang ◽  
Ion Sava ◽  
Angela Kruth ◽  
Klaus-Dieter Weltmann ◽  
...  
Keyword(s):  
High Voltage ◽  
Dielectric Spectroscopy ◽  
Polyimide Films ◽  
Electrical Discharges
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