Surge Protection Devices - Coursework Example

Background on Tasnee Tasnee is first join-stock industrial company that is fully owned privately. The company trades in the Saudi Arabia Stock Exchange Market and it has ventured into petrochemical industry as this is believed to be beneficial to the beneficiaries and shareholders of the company. Tasnee company has mainly focused in petrochemical and chemical industry in addition to its interest in engineering and mechanical industries. Tasnee provides management of industrial projects and markets products from industries, by ensuring that there is optimal utilization of natural resources and having competitive advantage in Saudi Arabia with it having the biggest share as a petrochemical producer in Arab States of the Gulf Cooperation Council. Electrical problems One of the major causes of electrical problems is as a result of the increased electronic equipment sensitivities. This problem is prevalent in petrochemical companies like Tasnee where use of electronic equipment is common. This problem is clearly illustrated using the US scenario where in 1993 power related problem was reported to have cost companies in the country an estimate of $26 billion(Jane Clemmenson,1993) a year in time lost and revenue. As a result of ever increasing b sensitivity and their application on the increase, the cost is on up word trend. Electric Power Research Institute (EPRI) made the projection of 70% of total power utility in the US would be controlled by power electronics. That was comparing to 30% in 1995(EPRI). Disturbance such as electrical noise or transient having magnitude in the range of two times rated operating voltage are a threat to the operation of micro-processor type of equipment, result to downtime and thus reducing the level production in petro chemical companies such as Tasnee that are used in petrochemical industry. Disturbances which are lower than double the voltage of operation are also problematic. A typical example being the case the logic voltage signal in a circuit is swamped resulting to errors in operation and equipment downtime. The advancement in technology level of microprocessor has brought about sub-micron features as well as integrated chips that are closely packed that have lower signal voltages so as to achieve increased operating speed. With a decreased signal voltage circuit density is increased but this assembly is easily damaged. These in essence means that application and facility engineers whose responsibility is to ensure there is maximum up-time and production are therefore not expected to rely what has happened in the past in the process of coming up with designs in the modern day process control environments. This is because with the modern equipment being more susceptible, past practices and experience become of little relevance. In order to maximize the productivity in petrochemical facilities there is need to use surge protections that are cost effective. Here electronic equipment manufacturers have recommended the use of surge protection devices this being on the basis of field operating experience. Surge protection devices (SPD) are very important in solving most of the problems experienced in petrochemical companies such Tasnee. The designs and performance criteria of SPD that can result to increased levels in terms of protection and reliability should include filter performance, the rating of surge current , Underwriters Laboratory (UL), Suppression Voltage Rating (SVR), and fuse installation, monitoring as well as the level of quality with regards to internal construction . The two surge protections that can be used are the parallel and series surge protectors. In series SPDs there is use of inductors that result to enhancement of their ability of reducing power disruption to lower levels in comparison to what parallel SPDs can achieve. With regards to large load applications series filters may not be recommended as they are not cost effective. For current rating the inductors usually used in Pi filter networks eventually become large with high cost. On the contrary parallel SPDs sizing does not correspond to a certain current or load and are found to be economical when they are used in the protection several loads simultaniously. Quality standards of Surge Suppression Devices The building entrance feeder surge protection conforms to NFPA 780 regulation in Tasnee facilities just as with many petrochemical establishments. According to this regulation the requirement is that devices that are well suited to protect the structure are to be fixed on electric and telephone service entrances. There is need for more electrical systems and utilization equipment protection against surge (Jane Clemmenson, 1993). Where large surge currents may be encountered diversion is to be done in two steps where the first is to be applied at the service entrance into the building. In case of a residual voltage that could as a result of this step, then another protective device located at the power panel that is to be at the computer room (Emerald Book, 1992). A combination of the two levels in protection linked to service entrance and branch panel location brings about reduction in the test wave that is recommended of magnitude C3-20Kv,3kA tolower than 200V which has no harm for sensitive loads that are rated at 120V. The provision of only building entrance feeder protection results to a let-through voltage of about 950V into a 277/480V system upon exposure to induced surges from lightning. This level of let-through voltage makes the system to be vulnerable to degradation and also could cause physical damage to electronic loads. Application of SPDs for facility wide protection Taking a system approach may be important in solving some electrical problems. In this approach electrical distribution layout is seen to be one system and there is attempt to maximize the reliability of equipment and productivity. By taking this approach there will be identification of critical, non-critical and the disturbance generating loads inside the facilities the internal distribution network will be reviewed and then the point of installation of the mitigation equipment will be determined. Installation of parallel SPDs at biding entrance feeder and panel board locations is the most effective and economical solution for a large number of loads protection. Through this approach there will be reduction in the cost of protection as multiple sensitive loads will be protected by a single device. In the facilities there are other critical loads that will be required to be given higher protection level. These loads seen as being essential in ensuring health and safety of occupants or help in critical controls in a processing line or operation. Series SPDs are recommended when it comes to protecting load of this nature in companies such as Tasnee. Some of the advantages that are associated with system approach are Can be considered as the lowest possible investment in equipment mitigation and protecting the facility By building entrance SPDs the facility will be protected from large external transients such as those caused by lightening By SPDs being bi-directional they ensure prevention of transient and noise interruptions emanating from feeding back in a system when installation is at distribution or branch panels With two levels of protection it is ensured that there is protection of sensitive loads from being damaged and also operational upset will be avoided Use of integrated SPD devices Use of integrated SPD devices is important in increasing protection level that is given so as to take care of unwanted surges and noise. By having surge suppressors directly connected to the bus of the electrical system will achieve the highest possible protection level. In comparison devices that are mounted by the side used in Tasnee, connection of the SPD to the bus ensures elimination of the necessity of having lead wires and thus reducing the let through voltage in the he margin of 50%. With surges being considered as being from high frequency disturbances, the inductance of wirings in the installation brings about an increase in let through voltage of the device. The result of having a lead length being installed on the let through voltage shows that an inch of lead length result to a let through voltage increase of 15v to 25V over the suppression performance given by the manufacturer. The lead length accounts for the highest proportion of the level of protection that is to be realized. Twisting of the installation wires comes in second is provision of protection whereby having the installation wires twisted brings about reduction in the area between wires and thus minimizing the mutual inductance effect. On the other hand an increase in the diameter of the installation wires does not bring about substantial effect. With inductance being linked to skin effect and being affected by the circumference of the wire, and with minimal effect on reducing of inductance being realized upon increasing the diameter of the installation conductor, using a wire of large diameter results to negligible improvement. Integrated surge suppression designs also have the benefits of eliminating cost due to field installation and the amount outboard wall space which is expensive that is needed for sidemounted SPD devices. Building Entrance Feeder SPD devices are to be installed just after the switch on the main breaker of the switch board as this is an optimal location that ensures that there is protection against external disturbances that include lightening. This location ensures that there is interception of any disturbance by the SPD reducing it to a lower level before it arrives at the distribution or the branch panel. By the disconnect switch being it becomes unnecessary for the building entrance feeder to be de-energized in the event that there is failure in SPD or it requires to be isolated for major testing. The size a suppressor measurement is at the surge current per phase with larger suppressors being rated at about 250kA per phase which are supposed to be installed at the service entrance as this can withstand high energy surges caused by lightening. Having a 250kA per phase surge rating will allow well over 25 years expectancy for an IEEE defined high exposure environment (IEEE Standards Collection, 1995). Lower surge rating may be used but this will compromise on reliability of the devices and their long term performance. For the case of an aerial structure, the 99.8 percentile recorded lightening stroke current would have a range of below 220kA. The level of surges conduction or inducement into the electrical system will be quite low their being a number of paths that the surge can travel through .This is why it is recommended by IEEE C62.42 that the C3(20Kv,10Ka) test wave used in test in SPDs is to be installed at building entrance feeders. SODs of Installation of Panelboard Surge Protection Devices It is recommended that consultants, specifiers and application engineers are to see to it that loads are connected to the same source. This ensures that there is separation of loads that generates disturbance is isolated from the electronic circuits that are affected by disruptions in power supply. A good example is where motors, HVAC installations and other loads that are non-linear will be isolated from equipment which is sensitive found within the petrochemical facilities. There is also need of installing smaller surge capacity SPDs in the range of 120Ka per phase at branch panel boards where power disturbance of lower energy are involved but the frequency of occurrence is much higher. With such level of surge current rating a life expectancy of 25 and above would be achieved. Where it calls for use of isolated ground systems, installation of an SPD would be required as this would ensure that any common mode surge type would be shunted to safety ground with using a disconnect switch as an optional. The extra let-through voltage that would result from having an increase in inductance resulting from a disconnecting switch wound having a range of 50V to 60V. This increased disturbance voltage may bring about process disruption. Considerations in Motor Control Center and Bus Way Installation There has been an increase in the need of having protection against power disturbance for motor control centers (MCC) power VFDs, electronic software starters, solid state overload relays, electronic metering and relaying equipment. Using MCC SPDs in building entrance feeder application would ensure there is first level of protection against external high energy disturbance. So as to have reduction in incoming power disturbance to a lower level, there is need for installation of a surge protector onto a bus in the main incoming structure. Suppose availability of space in the main structure is an issue of concern, then installation of the SPD can be done in a cell at the top of either the first or second structure. This set up would ensure that there is interception of external disturbances before entry into the electrical distribution system of the facility. What is currently in Tasnee conforms to the common convention where there is installation of lightening arrestors within MCCs that are used in building entrance applications. The level of protection resulting from devices in such arrangement is considered inadequate with regards to current loads which have high level of sensitivity. A typical case of let-through voltage for a surge arrester conforming to IEEE C62.41 C1 test wave of form (6000V,3000A) have a range of between 1500V and 2000Vwhich in essence is a lower level of protection by far in comparison to 800V let-through voltage for the case of a 480V WYE SPD. For the case of downstream MCCs it is recommended that it include a panel board feeding electronic loads where it can allow the SPD being integrated into the panel board or to be fixed between the transformer and panel board lugs. With such arrangement there will be prevention of power disturbances that could have had effect on the electronic loads that are connected to the panel board. Conclusion Electronic loads plays a critical role if competitive levels of production within current petroleum and petrochemical industry such as Tasnee. With the increased susceptibility it makes it necessary to provide protection any form of electrical disturbance. By having proper grounding, using SPDs at building entrance feeders while branch panel areas making use of cascaded network, it is found that having a facility wide king of approach and using a dataline protection in safeguarding communication devices will be cost effective when providing protection with regards to power disruptions. The level of protection that is to be realized is of higher magnitude upon integration of SPDs into a facility’s electrical distribution system. In comparison to the commonly used side mounted SPDs, integrated design ensures elimination of the inductance caused by installation wires and resulting to 50% lower let-through voltages. References Emerald Book, IEEE Std 1100-1992. Recommended Practice for Powering and Grounding Sensitive Electronic Equipment (ANSI) Jane Clemmenson,(1993). Collective Intelligence, Santa Rosa, CA, IEEE Spectrum June ’93 Electronic Power Research Initiative (EPRI) IEEE Standards Collection(1995), Surge Protection C62, Read More