A sequence of events recorder (SER)[1] is an intelligent standalone microprocessor based system, which monitors external inputs and records the time and sequence of the changes.[2][3] They usually have an external time source such as a GPS or radio clock. When wired inputs change state, the time and state of each change is recorded.
SERs enable rapid root cause analysis after multiple events have occurred due to the secure recording of the sequence of events in the order of occurrence. SERs are therefore utilized as a diagnostic tool to minimize plant downtime. SERs are often interfaced with a SCADA system, distributed control system or programmable logic controller (PLC).
SER reports are used by electrical engineers to analyze large and small electrical system blackouts. After the Northeast blackout of 2003, the North American Electric Reliability Corporation specified that electrical system data should be time-tagged to the nearest millisecond.
In 1984, the Tetragenics Company, a subsidiary of the Montana Power Company, introduced the first remote terminal unit (RTU) that time-tagged events to the nearest millisecond, and now there are also other RTUs with this capability. Digital protective relays and some PLCs now also include time-tagging to the nearest millisecond; SCADA systems that incorporate these devices provide SER functions without a dedicated SER device.
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Transcription
The cardiac conduction system consists of the following components: - The sinoatrial node, or SA node, located in the right atrium near the entrance of the superior vena cava. This is the natural pacemaker of the heart. It initiates all heartbeat and determines heart rate. Electrical impulses from the SA node spread throughout both atria and stimulate them to contract. - The atrioventricular node, or AV node, located on the other side of the right atrium, near the AV valve. The AV node serves as electrical gateway to the ventricles. It delays the passage of electrical impulses to the ventricles. This delay is to ensure that the atria have ejected all the blood into the ventricles before the ventricles contract. - The AV node receives signals from the SA node and passes them onto the atrioventricular bundle - AV bundle or bundle of His. - This bundle is then divided into right and left bundle branches which conduct the impulses toward the apex of the heart. The signals are then passed onto Purkinje fibers, turning upward and spreading throughout the ventricular myocardium. Electrical activities of the heart can be recorded in the form of electrocardiogram, ECG or EKG. An ECG is a composite recording of all the action potentials produced by the nodes and the cells of the myocardium. Each wave or segment of the ECG corresponds to a certain event of the cardiac electrical cycle. When the atria are full of blood, the SA node fires, electrical signals spread throughout the atria and cause them to depolarize. This is represented by the P wave on the ECG. Atrial contraction , or atrial systole starts about 100 ms after the P wave begins. The P-Q segment represents the time the signals travel from the SA node to the AV node. The QRS complex marks the firing of the AV node and represents ventricular depolarization: - Q wave corresponds to depolarization of the interventricular septum. - R wave is produced by depolarization of the main mass of the ventricles. - S wave represents the last phase of ventricular depolarization at the base of the heart. - Atrial repolarization also occurs during this time but the signal is obscured by the large QRS complex. The S-T segment reflects the plateau in the myocardial action potential. This is when the ventricles contract and pump blood. The T wave represents ventricular repolarization immediately before ventricular relaxation, or ventricular diastole. The cycle repeats itself with every heartbeat.
See also
References
- ^ "Sequence of events recorder". The Free Dictionary by Farlex.
- ^ "Sequence of events recorder facility for an industrial process control ..." Google Patents. 2010.
- ^ "Utility Communications Architecture (UCA) glossary". NettedAutomation.
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This page was last edited on 4 August 2023, at 03:03