Centrifugal compressor anti-surge control system modelling

<span>From the middle of XX century, natural gas is an important mineral, widely used in the energy sector. Transportation of natural gas is carried out via gas pipeline networks and compression stations. One of the key features which need to be implemented for any centrifugal gas compressor is a surge protection. This article describes the method and develops software application intended for simulation and study of surge protection system of a centrifugal compressor used in modern gas compression stations. Within the article research method, modelling environment’s block diagram, proposed algorithms and results are described. For surge cases control and prediction, Anti-surge control block implemented which based on practical experience and centrifugal compressor theory. To avoid complicated energy balancing differential equations the volumetric flow calculation algorithm proposed which is used in combination with Redlich-Kwong equation of state. Developed software’s adequacy test performed through modeling of one-stage gas compression scheme at rated speed with comparison of parameters with reference commercial software and verification of the anti-surge control system.</span>

Voltage characteristic as a parameter for surge arrester diagnosing

An alternative method for field MOV surge arresters diagnosing was observed, the controlled characteristic was the surge voltage of a gap arrester. The condenser that was connected in series with gap arrester was applied as voltage measurement sensor. Electrical aging of active elements (MOV), surge arrester insulation degradation and other types of electric faults causes to voltage increase at capacitor. The voltage value can be measured directly or the energy stored in capacitor can be transformed to electromagnetic signal and, then, registered remotely by specific radio transceiver. The capacitor connected in series with the surge arrester can also be used for leakage current limitation during all the life period of surge arrester. Shunted with a spark gap and presented as the low-current gap arrester with pre-sated discharge voltage glass (porcelain) pin-cap insulator can be the simplest, but reliable sensor. Taking into consideration modern technologies the surge arrester statement continuous monitoring system can be designed. It also allows locating the place of damaged arrester that is particularly true for remote maintenance of equipped with surge protection devices electrical

Protection of Centrifugal Compressor System

Surge and Choke phenomenon are the two unstable operating modes of a compression system. That surge mode occurs at mass flows below the so-called surge line, and the chock mode occurs at low pressure and high flow rate. These instability operation modes will reduce the compressor performance or even will be made damage to the compressor system [1-3]. There are many studies to prevent instability phenomenon by establishing control system to the ability to do that, but sometimes surge or chock phenomenon occurs although of this big effort. So, for this reason, the paper focus on the protection system, introduced to detect and prevent surge and shock stall occurrence to reduce damages possibility and keep the production at minimum losses. This can be achieved by setting the mass flow rate, pressure ratio, and operating speed in a predefined area. Depending on the data sets including measurements from compression systems of Sirt Oil Company, Libya, and performance characteristics curves and polynomial regression technique to define the operation area. The developed surge protection system was implemented on the Matlab Simulink program and presented in a simple form.

Behavioral studies of surge protection components

In our daily life, almost all the items we used, being a computer, television, lift or vehicle we drive consist of some kind of electrical or electronics component inside. The operation of these devices could be severely affected by lightning activity or electrical switching events, as there are more than 2000 thunderstorms in progress at any time resulting in 100 lightning flashes to ground per second. In practice, any device using electricity will subject to surge damages induced from the lightning or switching of heavy load. Surge protection device (SPD) is added at the power distribution panel and critical process loop to prevent damage subsequently cause plant shutdown. There are many questions raised on the SPD. How can this small device protect the equipment from large energy release by the lightning? What is inside the device? How does it work? This paper provides comprehensive detail in revealing the science and engineering behind the SPD, its individual component characteristic and how does it work. The technical information presented is limited to surge protection on equipment; surge protection for building structure will not be discussed here.

Surge protection of centrifugal compressors using advanced anti-surge control system

Centrifugal Compressors (CCs) are widely used equipment to transport the natural gas over long-distance pipelines from the gas processing facility to end consumers. Surge protection is of vital importance for such compressors to avoid costly damage to machine and production loss due to process interruption. In this paper, the dynamic behaviour of CCs has been studied during four critical scenarios: high header pressure, low suction pressure, startup of the new unit, and emergency shutdown of the unit. The dynamic simulation has been carried out using HYSYS software and validated with an industrial scale CC plant. The advanced Anti-Surge Control (ASC) consists of a split PID control in contrast to conventional PID control. The simulation results demonstrate the superior performance of advanced ASC over a conventional one for the severe surge in the event of high header pressure and low suction pressure. The occurrence of surge during start-up and the emergency shutdown was handled with the full open operation of the Anti-Surge Valve (ASV). The proposed algorithm has proved successful in protecting the compressor during fast transients of the operating point towards the surge limit line. The study is significant for the oil and gas plants and other process industry professionals for designing effective ASC systems.

Renewal of Middle Wave Transmitters in Slovak Republic

This paper deals with the replacement of middle wave transmitters in Slovak Republic. The original transmitters were based on class C vacuum tube fundamentals and were produced by the Czechoslovakian group company Tesla. Class C transmitters were transmitting reliably to this day, however, the lifespan of these transmitters was nearing its end, moreover the need for a better quality analog modulated signal has pushed for its replacement and therefore they were replaced by modern, highly efficient class D transmitters, while utilizing the original infrastructure consisting of antennas and power inputs. Due to differences in characteristic parameters, however minor, this caused some significant problems, with impedance matching. To resolve these problems, it was necessary to implement a newly designed IMU (Impedance Matching Unit), while also securing a lightning strike protection. This paper has proposed a possibility of lightning surge protection of middle wave transmitters. The original protection implemented with the installations of class C transmitters was consisted only of multiple spark gaps. This kind of protection may prove inefficient using new class D transmitters. The device described in this paper has been designed and successfully implemented on a middle wave transmitter in Čižatice. This transmitter is transmitting with 5 kW power on the antenna with the carrier frequency of 702 kHz. Since the implementation of our device, the transmitter reports no failures and continues to transmit safely.